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15-5 PH Stainless Steel

A precipitation hardening martensitic stainless steel. It is used in applications requiring better corrosion resistance and transverse properties compared to other similar martensitic grades.

The desired strength and toughness can be altered by temperate range in the heat treatment process. 15-5 is a variant of the older 17-4 chromium-nickel-copper precipitation hardening stainless steel. Both alloys exhibit high strength and moderate corrosion resistance. High strength is maintained to approximately 600°F. The 15-5 alloy was designed to have greater toughness than 17-4. This improved toughness is achieved by reduced delta ferrite content and control of inclusion size and shape.

17-4 PH Stainless Steel

Type 17-4PH® is a martensitic precipitation-hardening stainless steel that provides an outstanding combination of high strength and good corrosion resistance. ). The corrosion resistance of Type 17-4PH® is comparable to that of Type 304 stainless Steel in most media and superior to that of the hardenable 400 series stainless steels. 17-4 PH® maintains good mechanical properties at temperatures up to 600ºF (316ºC).

300 Series Stainless Steel

300 series, Stainless Steels have an austenitic crystalline structure, which is a face-centered cubic crystal structure. Austenite steels make up over 70% of total stainless steel production. They contain a maximum of 0.15% carbon, a minimum of 16% chromium and sufficient nickel and/or manganese to retain an austenitic structure at all temperatures from the cryogenic region to the melting point of the alloy.

The most widely used austenite steel is the 304, also known as 18/8 for its composition of 18% chromium and 8% nickel. 304 may be referred to as A2 stainless.

The second most common austenite steel is the 316 grade, also referred to as A4 stainless and called marine grade stainless, used primarily for its increased resistance to corrosion. 316 Stainless Steel is typically composed of 18% chromium and 10% nickel, commonly known as 18/10 stainless.

302 Stainless Steel

A steel with the same corrosion resistance as 304 Stainless steel, with slightly higher strength due to additional carbon.

303 Stainless Steel

A free machining version of 304 stainless steel via the addition of sulfur and phosphorus. Free machining materials require little power to cut, can be cut quickly, easily obtain a good finish, and do not wear the tooling much. Consequently, the factors that typically improve a material's performance often degrade its machinability.

304 Stainless Steel

Known as the most common stainless steel, 304 stainless steel contains both chromium and nickel as its main non-iron constituents. It is an austenite steel that is neither magnetic nor particularly electrically or thermally conductive. It has a higher corrosion resistance than regular steel and is widely used because of the ease in which it is formed into various shapes.

304 stainless steel is used for a variety of home and industry uses, such as screws, machinery parts, car headers, fabrics and other uses.

316 Stainless Steel

SAE 316 stainless steel is a molybdenum-alloyed steel. It is also called "marine-grade", due to it being the preferred steel for use in marine environments because of its greater resistance to pitting corrosion than other grades of steel.

The fact that it is negligibly responsive to magnetic fields means that it can be used in applications where a non-magnetic metal is required.

While 316 is not completely rust-proof, the alloy is more corrosion-resistant than other common stainless steels.

316L Stainless Steel

An extra low carbon grade of 316 Stainless Steel, generally used in marine applications and exclusively in the fabrication of reactor pressure vessels for boiling water reactors, due to its high resistance to corrosion.

316Ti Stainless Steel

A variant of type 316 that includes titanium for heat resistance. It is used in flexible chimney liners.

317 Stainless Steel

317 is a higher chromium, nickel and molybdenum version of 316 stainless designed principally for increased strength and corrosion resistance.

321 Stainless Steel

An austenitic chromium-nickel alloyed Stainless Steel. Similar to 304 but with lower risk of weld decay due to the addition of titanium.

400 Series Stainless Steel

The 400 series group of stainless steels has an 11 percent chromium and 1-percent manganese increase above the 300 series group. The 400 series is susceptible to rust and corrosion under some conditions. Heat-treating will harden the 400 series. The 400 series of stainless steels have higher carbon content, giving it a martensitic crystalline structure. This provides high strength and high wear resistance. Martensitic stainless steels aren’t as corrosion resistant as the austenitic types.

416 Stainless Steel

A ferritic and martensitic chromium alloyed Stainless Steel. It is easy to machine due to additional sulfur.

ABS Polymer

A common thermoplastic polymer. ABS, also known as Acrylanitrile Butadene Styrene, is stronger than pure polystyrene. The styrene gives the plastic a shiny, impervious surface. The polybutadiene, a rubbery substance, provides toughness even at low temperatures.

For the majority of applications, ABS can be used between −20 and 80 °C (−4 and 176 °F) as its mechanical properties vary with temperature.

Absolute Pressure

The difference between zero pressure (a perfect vacuum) and some known pressure. It may be arrived at by adding barometric pressure to gage pressure.

AC Voltage

Alternating current (AC), is an electric current in which the flow of electric charge periodically reverses direction, in contrast to direct current (DC), which only flows in one direction. AC is the form in which electric power is delivered to businesses and residences.

The usual waveform of alternating current in most electric power circuits is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. These types of alternating current carry information encoded onto the AC signal, such as audio or video.


Accuracy is the maximum operational set point deviation of a single sensor (a pressure, temperature, or flow switch) under one given set of environmental and operational conditions. It represents the combined error due to nonlinearity, nonrepeatability, and hysteresis expressed as a percentage of full scale output.


Also known as Delrin®, Acetal is an engineering thermoplastic used in precision parts requiring high stiffness, low friction and excellent dimensional stability.

Typical applications for include high performance engineering components such as small gear wheels, ball bearings, fasteners, and lock systems. The material is widely used in the automotive and consumer electronics industry.

Acrylic Resin

Acrylic resins are a group of related thermoplastic or thermosetting plastic substances derived from acrylic acid, methacrylic acid or other related compounds. Polymethyl acrylate is an acrylic resin used in an emulsed form for lacquer, textile finishes and adhesives.

Another acrylic resin is polymethyl methacrylate, which is used to make hard plastics with various light transmitting properties.

Acrylic resin is a common ingredient in latex paint. Interior and exterior latex paints offer better stain protection, greater water resistance, better adhesion, greater resistance to cracking and blistering, and resistance to alkali cleansers.

Active RTD

The active RTD detects and outputs a signal to the Electronics Module which is proportionate to the process media temperature plus heat added by the heater.

Actuation Point

The actuation point (sometimes called the set point) is the exact point at which the electrical circuit controlled by the switching element is opened (or closed) on increasing pressure or temperature.

The deactuation point is the opposite, or the point at which the electrical circuit is closed (or opened) on decreasing pressure or temperature.

Actuation Value

The difference between the actuation point and the deactuation point of a sensor. For instance, if a pressure switch reaches its actuation point and closes the snap action switch at 100 psi, it is in an actuated condition. If the pressure then drops and the switch deactuates (returns to its normal condition) at 90 psi, it is said to have a dead band of 10 psi.


An actuator is the mechanism of the switch or switch enclosure which operates the contacts. It is operated by a source of energy, typically electric current, hydraulic fluid pressure, or pneumatic pressure, and converts that energy into motion. An actuator is the mechanism by which a control system acts upon an environment. The control system can be simple (a fixed mechanical or electronic system), software-based (e.g. a printer driver, robot control system), a human, or any other input.

Adaptive Tuning

A self-tuning function that continuously monitors the dynamics of a process and makes adjustments to the control parameters to maintain a pre-determined setpoint.

Adjustable Range

The total range within which the actuation point (set point) of a sensor may be adjusted.

Agency Approval

Certification of conformity to the requirements of various independent testing agencies such as Underwriters Laboratories or the Canadian Standards Association.

Air Consumption

The maximum rate at which air is vented or bled from the device in order for the device to operate within its specifications.

Air Damped

A construction utilizing an air vane to achieve movement damping.

This vane is usually housed in a closed chamber to increase the damping action.

Air Flow

Air flow is a measurement of the amount of air per unit of time that flows through a particular device.

This amount of air can be measured by its volume or by its mass. Typically it is measured by volume, but for some applications it is necessary to measure it by mass, as air is a gas and therefore its volume can vary with temperature.


A point in a process if the value increases above (high alarm) or decreases below (low alarm), causes an action by an indicator or controller.

Alloy 20

Alloy 20 is a nickel–chromium–molybdenum stainless steel alloy developed for applications involving sulfuric acid. Its corrosion resistance finds many uses in the chemical, food, pharmaceutical, power generation, and plastics industries. Alloy 20 resists pitting and chloride ion corrosion and its copper content protects it from sulfuric acid.

Alloy 20 is not a stainless steel but a nickel alloy (ASTM). Alloy 20 is often chosen to solve the stress corrosion cracking problems which can occur with 316L stainless.


Average temperature coefficient of RTD resistance over the span of 0 to 100°C. Usually 0.00385 for DIN Standard 43760 platinum, and 0.003926 for 99.999% pure platinum.


A soft, nonmagnetic, ductile metal. Aluminum is remarkable for the metal's low density and for its ability to resist corrosion due to the phenomenon of passivation.

Structural components made from aluminium and its alloys are vital to the aerospace industry and are important in other areas of transportation and structural materials. The most useful compounds of aluminium, at least on a weight basis, are the oxides and sulfates.

Aluminum Alloy

Alloys in which aluminium is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc.

There are two principal classifications: casting alloys and wrought alloys, both of which are further subdivided as heat-treatable and non-heat-treatable.

Aluminium alloy surfaces will develop a white, protective layer of aluminium oxide if left unprotected by anodizing and/or correct painting procedures. In a wet environment, galvanic corrosion can occur when an aluminium alloy is placed in electrical contact with other metals with more negative corrosion potentials than aluminium, and an electrolyte is present that allows ion exchange.

Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys.

Ambient Conditions

The conditions around a device (humidity, pressure, temperature etc…).

Ambient Humidity

The maximum and minimum humidity that will surround a device during use. Also known as Relative Humidity.

Ambient Pressure

The pressure (usually, but not necessarily atmospheric) surrounding a pressure sensor.

Ambient Temperature

The maximum and minimum temperature that will surround the sensor during use and/or test.

American Bureau of Shipping

The American Bureau of Shipping (ABS) is a not-for-profit classification society with a mission to promote the security of life, property and the natural environment, primarily through the development and verification of standards for the design, construction and operational maintenance of marine-related facilities. ABS' core service is the provision of classification services through the development of standards called ABS Rules. These Rules form the basis for assessing the design and construction of new vessels and the integrity of existing vessels and marine structures. Services provided by ABS include classification, certification, Offshore and Energy Services, Statutory Services, Naval Vessel Standards and a Rapid Response Damage Assessment (RRDA) Program.


An electronic device which boots or increases a small signal to a higher level, usually for transmission, scale convenience, or noise immunity.

Analog Input

An analog input is a measurable electrical signal with a defined range that is generated by a sensor and received by a controller. The analog input changes continuously in a definable manner in relation to the measured property.

Analog Output

An analog output is a measurable electrical signal with a defined range that is generated by a controller and sent to a controlled device, such as a variable speed drive or actuator. Changes in the analog output cause changes in the controlled device that result in changes in the controlled process.

Analog to Digital Converter

A circuit or device that produces a digital output representing the magnitude of an analog input signal.


The situation where properties vary according to the direction in which they are measured.


A federation of trade associations, professional and scientific societies, and individual company members.

ANSI approves and serves as a clearinghouse for voluntary, nongovernmental American national standards.


The national trade association that provides information in the form of standards, bulletins, and recommended practices for the petroleum industry.

Apparent Shear Rate

The shear rate determined in capillary viscometers without making a Rabinowitsch correction for shear thinning.

Apparent Viscosity

The viscosity determined in capillary viscometry without making a Rabinowitsch correction for shear thinning.


ASCII (American Standard Code for Information Interchange) is a widely used code defined by ANSI (the American National Standards Institute). It represents the alphabet, the numeral digits, and many punctuation characters as 7-bit binary code. Packed ASCII, used in HART communications, is a 6-bit subset of ASCII which uses only upper case and omits many of the punctuation marks. It is employed so as to fit 4-bytes in a 3-byte field so that communications can be improved.


The American Society of Mechanical Engineers (ASME) is a professional association that, in its own words, "promotes the art, science, and practice of multidisciplinary engineering and allied sciences around the globe" via "continuing education, training and professional development, codes and standards, research, conferences and publications, government relations, and other forms of outreach." ASME is thus an engineering society, a standards organization, a research and development organization, a lobbying organization, a provider of training and education, and a nonprofit organization.


Abbreviation of American Society for Testing and Materials, an association for establishing standard testing and reporting procedures.


The Directive on Equipment and Protective Systems Intended for use in Potentially Explosive Atmospheres' (94/9/EC) entered into force on 1 March 1996.

The Directive is commonly referred to as the 'ATEX' Directive ('ATmospheres EXplosibles') but may also be called the ATEXEquipment Directive or ATEX 95.

Atmospheric Pressure

The actual weight per unit area of the earth’s atmosphere at a given locale and altitude. Atmospheric pressure at sea level is approximately 14.7 psi or 30 inches of mercury or 408 inches of water.


The gradual loss in intensity of any kind of beam through a medium. For instance, sunlight is attenuated by dark glasses, X-rays are attenuated by lead, and light and sound are attenuated by water.


A device that reduces the amplitude or power level of a signal without introducing appreciable distortion.

Auto/Manual Station

The controller function that allows the operator to select the Automatic or Manual control mode. In the automatic control algorithm the controller determines the control output. In the Manual mode, the operator determines the control output.


The ability to measure DC values of either polarity without the need to interchange test lead connections.


An automatic correction for offsets and drifts at zero input.

Average Responding

An AC measurement obtained using a DC instrument with a rectifying input circuit calibrated in terms of the corresponding RMS value. Accurate only for pure sine wave inputs.


The change in the position of an analog pointer from zero when the axis of the moving element moves from the vertical position to the horizontal position.

The balance is expressed as a percentage of the scale length.

Ball Valve

A form of quarter-turn valve which uses a hollow, perforated and pivoting ball to control flow through it. It is open when the ball's hole is in line with the flow and closed when it is pivoted 90-degrees by the valve handle. The handle lies flat in alignment with the flow when open, and is perpendicular to it when closed, making for easy visual confirmation of the valve's status.

Ball valves are durable, performing well after many cycles, and reliable, closing securely even after long periods of disuse. These qualities make them an excellent choice for shutoff applications. The ball valve's ease of operation, repair, and versatility lend it to extensive industrial use, supporting pressures up to 1000 bar and temperatures up to 752°F (500°C), depending on design and materials used.


The frequency span where a constant amplitude input will produce a meter reading within a specified limit (usually 3db). In controllers, the region around the setpoint where control occurs.


(2001) Ltd. (British Approvals Service for Electrical Equipment in Flammable Atmospheres) is the British national testing and certification authority for electrical equipment used in hazardous locations other than mines. Baseefa is a leading internationally recognized certification body for explosion pretected equipment, delivering both IECEx and ATEX certification to customers around the globe. Depending on the category of equipment involved, manufacturers are also required to install a quality system that ensures that a product that has been type examined will be faithfully replicated.


Digital transmission speed in bits per second.


A bellows or pair of bellows is a device constructed to furnish a strong blast of air.

In process control it can be used in a piping expansion joint: in this application, bellows are formed in series to absorb thermal movement and vibration in piping systems that transport high temperature media such as exhaust gases or steam.


A method for defining linearity. A straight line placed on a sensor output curve such that half the data points lie above and half below that line. The method for determining BFSL (Best Fit Straight Line), is the sum of least squares.

Bias Current

Current that flows out of an amplifier's input terminals which will produce a voltage drop across the source impedance. In a perfect amplifier this error term would be zero.

Bleed Diaphragm

A diaphragm assembly feature which contains a small orifice which allows a constant exhaust stream through the diaphragm. This constant exhausting increases the responsiveness and stability of the regulator by keeping the nozzle in a dynamic state.

Block and Bleed Manifold

A block and bleed manifold is a hydraulic manifold that combines one or more block/isolate valves and one or more bleed/vent valves into a single component, for interface with other components of a hydraulic system.

The purpose of the block and bleed manifold is to isolate the flow of fluid in the system, so the fluid from upstream of the manifold does not reach other components of the system that are downstream, then vent the remaining fluid from the system on the downstream side of the manifold. For example, a block and bleed manifold would be used to stop the flow of fluids to some component, then vent the fluid from that component’s side of the manifold, in order to effect some kind of work on that component.

Used in combustible gas trains in many industrial applications.

Bore Size

The diameter of a circular hole in a hollow tube or pipe produced by drilling, turning, or drawing.

Bourdon Tube

A thin-walled flattened tube of elastic metal bent into a circular arc whose application to certain pressure gauges and thermometers depends upon the fact that increase of pressure inside the tube tends to straighten it.


A metal alloy made of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties. It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure.

Brass is used for applications where low friction is required such as gears, bearings, valves; and plumbing and electrical applications. Brass is often used in situations in which it is important that sparks not be struck, such as in fittings and tools around explosive gases.

Breakdown Voltage Rating

The AC or DC voltage, which can be applied across the insulation portion of a transducer without arcing or conduction above a specific current value.

BSPP Connections

BSPP (British Standard Parallel Pipe) is most popular in the UK, Europe, Asia, Australia, New Zealand and South Africa.

It is a parallel thread fitting that uses a bonded seal ring to do the sealing. This bonded ring seal is sandwiched in-between a shoulder on the male fitting and the face of the female fitting and is squeezed in place. BSPP pressure gauges have a longer male thread and use a copper crush washer that is squeezed in between the bottom of the male fitting and the bottom of the female BSPP hole forming a pressure tight seal. No thread sealant is needed to form a seal.

BSPT Connections

BSPT (British Standard Pipe Thread) is similar to NPT except for one important difference. The angle across the flanks of threads (if you sliced the fitting in half long-ways and measured the angle from root to crest to root) is 55 degrees instead of 60 degrees as it is for NPT. Thus an NPT male will fit into a BSPT fitting or vice versa but they will not seal. This is a popular fitting in China and Japan but is very rarely used in North America unless the equipment to which it is attached was imported. Thread sealant is needed to seal the male and female fitting together.


The quantity of thermal energy required to rise one pound of water 1°F at or near its maximum density (39.1°F) (1055J).


The input impedance of a measuring circuit (expressed in ohms) or the load on the secondary of a transformer (expressed in volt-amps or watts). In potential or current transformers, burden is the maximum load the transformer can support while operating within its accuracy rating.

Bureau Veritas

Bureau Veritas is a global company involved in testing, inspection and certification services. Bureau Veritas offers services and solutions to ensure that their clients' assets, products, infrastructure and processes meet standards and regulations in terms of quality, health and safety, environmental protection and social responsibility. As of the end of 2014, the group has more than 1,400 offices and laboratories located in 140 countries.

Burst Pressure

The specified pressure which will rupture the sensing element but not the sensor case.


Override control is a control method that is used to select the most pertinent information from a set of indicators to control the output. This situation usually arises when two or more variables in a system have to be controlled so that they do not surpass certain limits. These constraints usually arise from safety concerns, issues with efficiency, and economics of the process.

Override controls do not replace other types of dynamic controllers (e.g. PID), instead these controllers are used in case where a choice must be made between inputs, such as emergencies that fix problems.

Limits (maximums or minimums) are used in order to select an output.


(1) A test during which known values of pressure are applied to the device and corresponding output readings are recorded under specified conditions.

(2) Adjustment of an instrument to standards of known accuracy and stability.

Calibration Cycle

Pressure calibration in both a descending and ascending mode.

Carbon Steel

Steel in which the main interstitial alloying constituent is carbon.

Trace impurities of various other elements can have a significant effect on the quality of the resulting High-Carbon steel. Trace amounts of sulfur in particular make the steel brittle and crumbly at working temperatures.

Manganese is often added to improve the hardenability of low-carbon steels. Low-Carbon steel is the most common form of steel because its price is relatively low while it provides material properties that are acceptable for many applications. Low-carbon steel is malleable and ductile. Also contains less carbon than other steels and are easier to cold-form, making them easier to handle.

Mild Carbon steel has a relatively low tensile strength, but it is cheap and easy to form; surface hardness can be increased through carburizing. It is often used when large quantities of steel are needed, for example as structural steel.

Cast Iron

A group of iron-carbon alloys with a carbon content greater than 2%. Carbon and silicon are the main alloying elements. Iron alloys with less carbon content are known as steel. Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are used in pipes, machines and automotive industry parts. It is resistant to rust.


A substance that changes the rate of a chemical reaction without itself undergoing a permanent change or becoming part of the molecular composition of the product.


The China Compulsory Certificate mark, commonly known as a CCC Mark, is a compulsory safety mark for many products imported, sold or used in the Chinese market. It was implemented on May 1, 2002 and became fully effective on August 1, 2003. It is the result of the integration of China's two previous compulsory inspection systems, namely "CCIB" (Safety Mark, introduced in 1989 and required for products in 47 product categories) and "CCEE" (also known as "Great Wall" Mark, for electrical commodities in 7 product categories), into a single procedure. The CCC mark is required for both Chinese manufactured and foreign imported products.


The CE mark (or formerly EC mark) is a mandatory conformity marking for certain products sold within the European Economic Area (EEA).vThe CE marking is also found on products sold outside the EEA that are manufactured in, or designed to be sold in, the EEA. The CE marking is the manufacturer's declaration that the product meets the requirements of the applicable EC directives.


Committee responsible for European standardization in the area of electrical engineering. Together with ETSI (telecommunications) and CEN (other technical areas), it forms the European system for technical standardization.

Standards harmonised by these agencies are regularly adopted in many countries outside Europe which follow European technical standards. The current members of CENELEC include Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Macedonia, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Spain, Slovakia, Slovenia, Sweden, Switzerland, Turkey and the United Kingdom. Albania, Belarus, Bosnia/Herzegovina, Egypt, Georgia, Israel, Jordan, Libya, Moldova, Montenegro, Morocco, Serbia, Tunisia and Ukraine are currently "affiliate members" with a view to becoming full members. CENELEC has cooperation agreements with Canada, China, South Korea, Japan, an informal agreement with the USA and ongoing discussion on a cooperation agreement with Russia.

Although CENELEC works closely with the European Union, it is not an EU institution.


The fluid with which the temperature sensing probe is filled.

Chrome Plating

A technique of electroplating a thin layer of chromium onto a metal or plastic object. The chromed layer can be decorative, provide corrosion resistance, ease cleaning procedures, or increase surface hardness. Sometimes a less expensive imitator of chrome may be used for aesthetic purposes.

Chrome Steel

A class of non stainless steels such as AISI 52100 or DIN 5401 which are used for applications such bearings, tools, drills and utensils. Corrosion Resistant.

Chromoly Steel

A family of SAE steel grades. Alloying elements include chromium and molybdenum.

They have an excellent strength-to-weight ratio and are considerably stronger and harder than standard 1020 steel, but are not easily welded (need pre and post weld thermal treatment to avoid cold cracking). While these grades of steel do contain chromium, it is not in great enough quantities to provide the corrosion resistance found in stainless steel. One of the characteristics of this class of steel is the ability to be case hardened by carburization of the surface.

Examples of applications include tubes for transportation of pressurized gases. The core of the material retains its bulk properties, while the outer surface is significantly hardened to reduce wear and tear, which makes this grade of steel an excellent material for such uses as gears, piston pins, and crankshafts.

Coefficient of Friction

A measure of the resistance to sliding of one surface in contact with another.

Cold Junction Compensation

A correction applied to thermocouple measurements to compensate for the temperature of the Thermocouple wire connections, so the temperature reading is only the result of the measuring thermocouple junction.

Common-Mode Rejection

The ability of a circuit or meter to reject a signal that appears at both input terminals with respect to ground.

Common-Mode Voltage

An AC or DC voltage which appears between the signal lines and circuit ground or earth.


The addition of specific material or device(s) to counteract a known error.


The reciprocal of electrical resistivity, Conductivity measures a material's ability to conduct an electric current.

Conduit (Electrical)

A tube used to protect and route electrical wiring in a building or non-building structure. Electrical conduit may be made of metal, plastic, fiber, or fired clay. Most conduit is rigid, but flexible conduit is used for some purposes. Its use, form, and installation details are often specified by wiring regulations, such as the US National Electrical Code (NEC) and other building codes.

Conduit (Fluid Conveyance)

A tubular section or hollow cylinder, usually but not necessarily of circular cross-section, used mainly to convey substances which can flow — liquids and gases (fluids), slurries, powders and masses of small solids. It can also be used for structural applications; hollow pipe is far stiffer per unit weight than solid members.


The process of setting parameters, values and data which will determine how a device will operate.

Conformity Error

The difference between the actual response and the ideal response to a particular stimulus.

Control Mode

Type of control used in a feedback control system.

One mode is proportional control.

Two mode is proportional plus integral (reset) or derivative (rate).

Three mode is proportional, integral and derivative (PID).

Control Output

The output signal from a controller to the manipulated variable in response to input signals from the controlled variable.


A device which manipulates one process variable (RPM, Heat, etc.) to result in a stable condition of a second (controlled) variable (pressure, temperature, etc).

Conversion Rate

The number of analog-to-digital conversions performed per second by a digital instrument.


The major applications of copper are in electrical wires, roofing, plumbing and industrial machinery. Copper is mostly used as a pure metal, but when a higher hardness is required it is combined with other elements to make an alloy such as brass and bronze. Despite competition from other materials, copper remains the preferred electrical conductor in nearly all categories of electrical wiring.

Copper wire is used in power generation, power transmission, power distribution, telecommunications, electronics circuitry, and countless types of electrical equipment. Many electrical devices rely on copper wiring because of its multitude of inherent beneficial properties, such as its high electrical conductivity, tensile strength, ductility, creep (deformation) resistance, corrosion resistance, low thermal expansion, high thermal conductivity, solderability, and ease of installation. Integrated circuits and printed circuit boards increasingly feature copper in place of aluminium because of its superior electrical conductivity. Electromagnets, vacuum tubes, cathode ray tubes, and magnetrons in microwave ovens use copper, as do wave guides for microwave radiation.

Copper Alloy

Metal alloys that have copper as their principal component.

They have high resistance against corrosion.

The best known traditional types are bronze, where tin is a significant addition, and brass, using zinc instead.


The tendency of a solid material to move slowly or deform permanently under the influence of mechanical stresses. It can occur as a result of long-term exposure to high levels of stress that are still below the yield strength of the material. Creep is more severe in materials that are subjected to heat for long periods, and generally increases as they near their melting point.

Crest Factor

The ratio of the maximum (crest) value of a periodic function (AC voltage or current) to its RMS value.

Critical Set Point

The critical set point is the set point of the unit which is held to the closest tolerance. It can be either the actuation (increasing) or deactuation (decreasing) point.

CRN (Canadian Registration Services)

Statutory Declaration, Registration of Fitting (Technical Standards and Safety Act, 2000, and Regulations for Boilers and Pressure Vessels and CSA Standard B51)

CSA (Canadian Standards Association)

A nonprofit voluntary association engaged in standards development and certification activities. A CSA certified electrical product conforms to applicable requirements of the Canadian Electrical Code. Representative prototypes are tested prior to certification and CSA maintains a production surveillance program to ensure continuing conformity.


A commonly used refrigerant in cryogenic applications. CTFE has a carbon-carbon double bond and so can be polymerized to form polychlorotrifluoroethylene or copolymerized to produce the plastic ECTFE.

Current Loop

A two-wire loop in which the current through the wires is maintained according to a controlling device, usually a two-wire transmitter.

The advantages of a current loop are longer distance signal transmission, better noise immunity, and the ability to power the two-wire transmitter throughout the same two wires.

The most common current loop is 4 to 20 mA.

Cycle Time

The time usually expressed in seconds for a controller to complete one on/off cycle.


An analog function that modifies the response time of the transmitter to smooth the output signal in the presence of a rapidly varying input signal.

DC Voltage

The unidirectional flow of electric charge. Direct current is produced by sources such as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through semiconductors, insulators, or even through a vacuum as in electron or ion beams. The electric current flows in a constant direction, distinguishing it from alternating current (AC).


The Deactuation Point is the opposite of the Actuation Point, or the point at which the electrical circuit is closed (or opened) on decreasing pressure or temperature.

Dead Bank

The range through which input can be varied without initiating observable change in output. (There is a separate and distinct input-output relationship for increasing and decreasing signals.)

Dead Volume

The volume of the pressure port of a transducer at room temperature and ambient barometric pressure.


The difference between the actuation point and the deactuation point of a sensor. For instance, if a pressure switch reaches its actuation point and closes the snap action switch at 100 psi the switch is in an actuated condition. If the pressure then drops and the switch deactuates (returns to its normal condition) at 90 psi, it is said to have a dead band of 10 psi.

Det Norske Veritas

Det Norske Veritas is an international certification body and classification society with main expertise in technical assessment, advisory, and risk management. DNV is a reference in renewable, alternative and conventional energy. It is the world's largest technical consultancy to onshore and offshore wind, wave, tidal, and solar industries, as well as the global oil & gas industry - 65% of the world’s offshore pipelines are designed and installed to DNV's technical standards. DNV is involved in risk-management, technical advisory, counselling, testing, assessment and the classification and verification of processes in Maritime, Business, Software Development, Energy and the Oil and Gas sector.


A sheet of a semi-flexible material anchored at its periphery and most often round in shape. It serves either as a barrier between two chambers, moving slightly up into one chamber or down into the other depending on differences in pressure, or as a device that vibrates when certain frequencies are applied to it.

Dielectric Strength

The voltage that can be sustained without breakdown.

Differential Pressure

The difference between a reference pressure and a variable pressure.

Digital Input

Auxiliary input to an indicator or controller which performs a function via switch closure or opening.

Typically used to reset a latched alarm, or to duplicate a front panel function such as selection of automatic or manual control modes.

Digital Output

An output signal, which represents the size of a stimulus or input in the form of a series of discrete quantities


A set of German technical standards.

Commonly used to specify panel meter sizes.

Direct Acting

Control output action which increases as the process variable increases. In the case of an alarm, a direct acting alarm has its relay activated in an alarm condition.


Disogrin® 7695 and 9250 are Simrit's proprietary compounds used for fluid power seals. Disogrin® 7695 has been especially developed to be water, acid and base resistant. While many polyurethane seals are vulnerable to hydrolysis or degradation by water, seals made of Disogrin® 7695 are compatible with both mineral oils and water, fitting a more diverse range of applications.

Disogrin® 7695 is specially suited for biodegradable fluid applications common in forestry, landscaping, agriculture, marine, oilfield and water treatment.

Disogrin® 7695 is compatible with water and resistant to hot water up to 250 degrees F, making it a possible alternative to chloroprene and EP rubbers. It is compatible with hot vegetable and mineral oil based fluids and resistant to acidic and basic solutions (pH 2-13) up to 220 degrees Fahrenheit. Disogrin® 9250 is more robust, wear-resistant iteration that withstands higher pressure and lasts longer. Disogrin® 9250 is used in Simrit rod seals, piston seals, cover seals, wipers and O-rings. It has an improved compression set, is resistant to high pressure extrusion, improved fluid compatibility and high heat resistance. The increased resistance to wear and abrasion allows for greater longevity of use.


A device which monitors and displays the condition of a process variable without exerting any control action. Indicators may be equipped with alarms or other auxiliary outputs.


An undesired change that takes place in a process that tends to affect adversely the value of a controlled variable.

Double Break Switching Element

A double break switching element has two isolated circuits; one normally open and one normally closed, the four terminals facilitate wiring.

DPDT (Double Pole Double Throw)

A DPDT switching element has six electrical terminals. In simple terms, it is two SPDT switching elements operating simultaneously at the same settings. This type of switch can handle two independent circuits without using a relay.


An undesired change in output over a period of time, of which change is not a function of the measurand.


The deviation of output from set point pressure as downstream flow requirements change.

Dual Seal

The imminent Canadian national code adoption of NEC 2009 required process instrumentation such as flow, level and pressure gauges, meters and switches, to certify their devices to the ANSI/ ISA 12.27.01 standard. Supplying a device with a nameplate labeled “Dual Seal” or “Single Seal” meets the NEC 2009 code, and permits an end-user installer to eliminate a costly secondary seal.

Dual Setting

A dual setting pressure sensor has two independently adjustable electrical switches that are actuated by a shared pressure source. Equivalent to two field adjustable pressure switches in one package.

Dual-Slope Conversion

An analog to digital conversion technique which can provide high noise rejection.

Ductile Iron

A type of cast iron.

While most varieties of cast iron are brittle, ductile iron has much more impact and fatigue resistance, due to its nodular graphite inclusions. Much of the annual production of ductile iron is in the form of ductile iron pipe, used for water and sewer lines. It competes with polymeric materials such as PVC, HDPE, LDPE and polypropylene. Because these alternatives are significantly lighter and more flexible than steel or ductile iron they consequently require protection from physical damage.

Ductile iron is specifically useful in many automotive components, where strength needs surpass that of aluminum but does not necessarily require steel. Other major industrial applications include oil well pumps. In the wind power industry, nodular cast iron is used for hubs and structural parts like machine frames. Nodular cast iron is suitable for large and complex shapes and high (fatigue) loads.


Duplex communications means communications in both directions (as opposed to Simplex, which is communications in one direction only). Concurrent transmission and reception.

Contrasts with half-duplex (one direction at a time).


A polymer with viscoelasticity and very weak inter-molecular forces. The term, which is derived from elastic polymer, is often used interchangeably with the term rubber, although the latter is preferred when referring to vulcanisates.

Elastomers are amorphous polymers existing below their glass transition temperature, so that considerable segmental motion is possible. At ambient temperatures, rubbers are thus relatively soft and deformable.

Their primary uses are for seals, adhesives and molded flexible parts. Application areas for different types of rubber are manifold and cover segments as diverse as tires, shoe soles as well as dampening and insulating elements. Elastomers are usually thermosets (requiring vulcanization) but may also be thermoplastic.

Electric Field

A component of the electromagnetic field. It is a vector field, and it is generated by electric charges or time-varying magnetic fields.

The concept of an electric field was introduced by Michael Faraday.

Electrical Contacts

An electrical circuit component found in electrical switches, relays and breakers. It is composed of two pieces of electrically conductive metal that pass electrical current or insulate when the gap between them is closed or open. The gap must be an insulating medium of air, vacuum, oil, or other electrically insulating fluid.

Contacts may be operated by humans in pushbuttons and switches, by mechanical pressure in sensors or machine cams, and electromechanically in relays.

Contact materials are usually composed of superior conduction materials such as silver or gold. Cheaper metals may be used to reduce costs for the main contact bump and plated with superior metals. The contact arms are typically spring metals to allow operation motion without breaking.

Electrical Current

A flow of electric charge. In electric circuits this charge is often carried by moving electrons in a wire. It can also be carried by ions in an electrolyte, or by both ions and electrons such as in a plasma.

Electrical Current is measured in amperes using a device called an ammeter.

Electric currents cause Joule heating, which creates light in incandescent light bulbs. They also create magnetic fields, which are used in motors, inductors and generators.

Electrical Filter

A device to sort desired result from undesired. Electrically, a selective circuit which passes through certain frequencies, while attenuating or rejecting others.

Electrical Load

An electrical component or portion of a circuit that consumes electric power.

This is opposed to a power source, such as a battery or generator, which produces power.

In electric power circuits examples of loads are appliances and lights. The term may also refer to the power consumed by a circuit.

The term is used more broadly in electronics for a device connected to a signal source, whether or not it consumes power. If an electric circuit has an output port, a pair of terminals that produces an electrical signal, the circuit connected to this terminal (or its input impedance) is the load. For example, if a CD player is connected to an amplifier, the CD player is the source and the amplifier is the load.

Electrical Output

The current, voltage, power, or signal produced by an electrical or electronic circuit or device.

Electro Motive Force

An electrical potential difference which produces or tends to produce an electric current.

Electromagnetic Compatibility

The ability of equipment or a system to function as designed in its electromagnetic environment without introducing intolerable electromagnetic disturbances to that environment, or being affected by electromagnetic disturbances in it.

Electromagnetic Energy

The energy of electromagnetic radiation. The SI unit of radiant energy is the joule (J). The quantity of radiant energy may be calculated by integrating radiant flux (or power) with respect to time.

The term is used particularly when electromagnetic radiation is emitted by a source into the surrounding environment. This radiation may be visible or invisible to the human eye.

Electrostatic Discharge

The sudden flow of electricity between two electrically charged objects caused by contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by tribocharging or by electrostatic induction. The ESD occurs when differently-charged objects are brought close together or when the dielectric between them breaks down, often creating a visible spark. ESD can create spectacular electric sparks (lightning is a large-scale ESD event), but also less dramatic forms which may be neither seen nor heard, yet still be large enough to cause damage to sensitive electronic devices.

Other forms of ESD include corona discharge from sharp electrodes and brush discharge from blunt electrodes.

ESD can cause a range of harmful effects of importance in industry, including gas, fuel vapour and coal dust explosions, as well as failure of solid state electronics components such as integrated circuits. These can suffer permanent damage when subjected to high voltages. Electronics manufacturers therefore establish electrostatic protective areas free of static, using measures to prevent charging, such as avoiding highly charging materials and measures to remove static such as grounding human workers, providing antistatic devices, and controlling humidity.


a "super-alloy" consisting of 39-41% Cobalt, 19-21% Chromium, 14-16% Nickel, 11.3-20.5% Iron, 6-8% Molybdenum, and 1.5-2.5% Manganese.

It is used to make springs that are corrosion resistant and exhibit high strength, ductility, and good fatigue life.

EMC Directive

The branch of electrical sciences which studies the unintentional generation, propagation and reception of electromagnetic energy with reference to the unwanted effects (electromagnetic interference, or EMI) that such energy may induce. The goal of EMC is the correct operation, in the same electromagnetic environment, of different equipment which use electromagnetic phenomena, and the avoidance of any interference effects.

Several international organizations work to promote international co-operation on standardization (harmonization), including publishing various EMC standards. Where possible, a standard developed by one organization may be adopted with little or no change by others. This helps for example to harmonize national standards across Europe. Standards organizations include: IEC, CISPR, ACEC, ISO, CEN, CENELEC, ETSI, FCC, SAE, BSI, and VDE.


Electrical and magnetic noise imposed on a system. There are many possible causes, such as switching AC power on inside the sine wave.

EMI can interfere with the operation of controls and other devices.

End Point

The output at zero pressure and full-scale pressure.

Environmental Conditions

All conditions to which a transducer may be exposed during shipping, storage, handling, and operation.


Ethylene propylene rubber is an elastomer prepared from ethylene and propylene monomers.

Ethylene propylene rubber has a temperature range of -50°C to +120°/150°C (-60°F to +250°/300°F), depending on the curing system. Special grades can even see higher temperatures.

EPDM rubber is used in seals, glass-run channels, radiators, tubing, belts, electrical insulation, and O-rings. EPDM is also used as a medium for water resistance in electrical cable-jointing, geomembranes, rubber mechanical goods, plastic impact modification, thermoplastic, vulcanizates, and many other applications.

Epoxy Coating

Two part epoxy coatings were developed for heavy duty service on metal substrates and use less energy than heat-cured powder coatings. These systems dry quickly providing a tough, protective coating with excellent hardness. Their low volatility and water clean up makes them useful for factory cast iron, cast steel, cast aluminium applications and reduces exposure and flammability issues associated with solvent-borne coatings.

They are usually used in industrial and automotive applications since they are more heat resistant than latex-based and alkyd-based paints. Epoxy paints tend to deteriorate, known as "chalking out" under prolonged UV exposure. Fusion Bonded Epoxy Powder Coatings (FBE) are extensively used for corrosion protection of steel pipes and fittings used in the oil and gas industry, potable water transmission pipelines (steel), and concrete reinforcing rebar. Epoxy coatings are also widely used as primers to improve the adhesion of automotive and marine paints especially on metal surfaces where corrosion (rusting) resistance is important.


The difference between the value indicated by the transducer and the true value of the pressure being sensed.

Error Band

The allowable deviation of output from specific reference norm


The voltage supplied by an indicator or controller to a transducer to provide its proper operating conditions.

Expanded Scale

An arrangement that expands a specific portion of an overall range to occupy a larger portion of the full-scale length than it normally would.

Explosion Proof

Having the ability to contain an explosion within the sensor or housing if it were to occur.

Factory Set

Switch which can be set only at the factory to customer’s requirements.


Assuming a safe operating mode in the event of a failure.

Failure Mode Alarm

A transmitter output function that drives the analog output of the transmitter to a selectable value in the event of a failure of the electronics or sensor element. The output may be driven high, low, or assume the last valid value read by the transmitter.


Occurs when outputs of a system are routed back as inputs as part of a chain of cause-and-effect that forms a circuit or loop. The system can then be said to feed back into itself. The notion of cause-and-effect has to be handled carefully when applied to feedback systems.


A type of fiber reinforced plastic where the reinforcement fiber is specifically glass fiber. The glass fiber may be randomly arranged, flattened into a sheet or woven into a fabric. The plastic matrix may be a thermosetting plastic, vinylester or a thermoplastic.

Fiberglass is a strong lightweight material and is used for many products. Although it is not as strong and stiff as composites based on carbon fiber, it is less brittle, and its raw materials are much cheaper. Its bulk strength and weight are also better than many metals, and it can be more readily molded into complex shapes. Applications of fiberglass include aircraft, boats, automobiles, septic tanks, water tanks, pipes, cladding and casts.

Fibre-reinforced plastic

A composite material made of a polymer matrix reinforced with fibers. The fibres are usually glass, carbon, aramid, or basalt. Rarely, other fibres such as paper or wood or asbestos have been used. The polymer is usually an epoxy, vinylester or polyester thermosetting plastic.

FRPs are commonly used in the aerospace, automotive, marine and construction industries. Fibre-reinforced plastics are best suited for any design program that demands weight savings, precision engineering, finite tolerances, and the simplification of parts in both production and operation. A moulded polymer artefact is cheaper, faster, and easier to manufacture than cast aluminium or steel artefact, and maintains similar and sometimes better tolerances and material strengths.

Field Adjustable

A pressure switch design that provides for adjustment of set points in the field.

Field Set

A pressure switch design that provides for field adjustment of set points.

Adjustment is accomplished by turning an adjustment screw located inside of pressure port prior to installation. After unit is installed, set points can be adjusted by removing pressure fittings to access adjustment screw.


Fieldbus is the name of a family of industrial computer network protocols used for real-time distributed control, standardized as IEC 61158. A complex automated industrial system — such as manufacturing assembly line — usually needs a distributed control system—an organized hierarchy of controller systems—to function.

Fire Resistant

A device that is designed with a high melting point barrier (steel) that will prevent full flow of sensed flammable fluid from feeding an externally caused fire.


A flange is an external or internal ridge, or rim (lip), for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel.

Flow Capacity

The Rate which a volume will pass forward through a given device within a unit of time while variables are undergoing a change.

Typically expressed in SCFM for gases or GPM for Liquids.

Flow Switch

A mechanical switch that is switched on or off in response to the flow or non-flow of a fluid such as air or water.

A flow switch typically operates through the use of a paddle which gets displaced due to the force of fluid moving past it. Flow switches find application in the detection of fluid flow and measurement of fan speeds.

A sail switch might be used to protect a central heating system electric heating element from being energized before the air flow from the blower is established. Sail switches might also be used to alarm if a ventilation fan in a hazardous location fails and air flow has stopped. For some HVAC systems, a sail switch can activate an electronic air cleaner, a humidifier, or other equipment in response to airflow from the system fan.


A substance that continually deforms (flows) under an applied shear stress. Fluids are a subset of the phases of matter and include liquids, gases, plasmas and, to some extent, plastic solids. Fluids can be defined as substances that have zero shear modulus or in simpler terms a fluid is a substance which cannot resist any shear force applied to it.


The trademarked brand name for the line of electronics coolant liquids sold commercially by 3M. It is an electrically insulating, stable fluorocarbon-based fluid which is used in various cooling applications.

It is mainly used for cooling electronics. Different molecular formulations are available with a variety of boiling points, allowing it to be used in "single phase" applications where it remains a liquid, or for "two-phase" applications where the liquid boils to remove additional heat via evaporative cooling. Fluorinert is used in situations where air will not carry away enough heat, or where airflow is so restricted that some sort of forced pumping is required.

Fluorinert may be harmful if inhaled and care should be taken to avoid contact with eyes and skin. Use should be constrained to closed systems and reduced volumes as fluorinated oils have a very high global warming potential and a long atmospheric lifetime.


A special purpose fluorocarbon-based synthetic rubber.

It has wide chemical resistance and superior performance, especially in high temperature application in different media. The performance of fluoroelastomers in aggressive chemicals depends on the nature of the base polymer and the compounding ingredients used for moulding the final products (e.g. O-rings, shaft seals). This performance can vary significantly when end-users purchase polymer containing rubber goods from different sources.

Fluoroelastomers are generally compatible with hydrocarbons, but incompatible with ketones such as acetone and organic acids such as acetic acid.

Fluorolube Oil

Fluorolube® oils are liquid lubricants that deliver long-lasting lubrication for metallic surfaces (except copper, aluminum and magnesium) in applications requiring stability and performance in strongly acidic and/or oxidizing environments.

They are saturated, hydrogen-free, low-molecular weight polymers of chlorotrifluoroethylenes (CTFE) that combine high-temperature performance, non-flammability and chemical inertness under many demanding conditions. Available in a range of viscosities, Fluorolube oils are compatible with chlorine, oxygen, hydrogen peroxide, red fuming nitric acid and other strong oxidizing agents. They consist of about 80 percent combined fluorine and chlorine and are nonflammable.

Fluorolube oils are used in chemical manufacturing, electrical applications, hydraulic fluids, instrument fill fluids, nuclear industry, pulp and paper industry, steel industry, and Water and Wastewater Treatment.


FM Approved units are currently unavailable. Please choose CSA as both Canadian and United States standards are covered under the certification from CSA Lab

Fomblin Oil

Fomblin® PFPE are fluorinated lubricants that work well when aggressive chemical environments, high temperatures or wide working-temperature ranges are involved.

Fomblin® PFPE lubricants are engineered for those applications where heat, chemicals, solvents, corrosion, toxicity, flammability, and service life present lubrication problems. While Fomblin® PFPE lubricants can be used in their original form, they are often formulated into greases for specific applications in the chemical, electronic, military, nuclear, data processing, and other industries in need of high performance lubrication. Fomblin oils exhibit excellent electrical resistance, are non–reactive with metal, plastic, elastomers and rubber, non-flammable and environmentally safe.


1) The frequency of free (not forced) oscillations of the sensing element of a fully assembled sensor.

2) An output in the form of frequency which varies as a function of the applied pressure.


Full Scale Pressure Range. The design maximum value of input pressure that the transmitter is designed to measure.

Full Scale Output

The electrical output of the pressure device with full scale pressure applied.

Usually expressed in electrical units (mV/V, V, mA).

Full Scale Pressure

The maximum pressure under which applicable performance specifications apply.

Full Scale Value

The arithmetic sum of the two end-scale values (may not apply to some specialized meters, such as power factor).

When zero is not on the scale, the full-scale value is the higher end-scale value. Examples: Scale Full Scale Value 0-200V 200V 25-0-175V 200V 250-0-250V 500V 60-160V 160V


The ratio of the change in output to the change in input, which caused it.

Gain Adjustment

Means of adjusting the full scale output of an amplified transducer.


The process of applying a protective zinc coating to steel or iron, to prevent rusting. The most common method is hot-dip galvanization, in which parts are submerged in a bath of molten zinc.

Galvanizing protects in two ways: it forms a coating of corrosion-resistant zinc which prevents corrosive substances from reaching the more delicate part of the metal and the zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc. Although galvanizing will inhibit attack of the underlying steel, rusting will be inevitable, especially if exposed to the natural acidity of rain. Marine and salty environments also lower the lifetime of galvanized iron because the high electrical conductivity of sea water increases the rate of corrosion primarily through converting the solid zinc to soluble zinc chloride which simply washes away. Galvanized steel can last for many years if other means are maintained, such as paint coatings and additional sacrificial anodes. The rate of corrosion in non-salty environments is mainly due to levels of sulfur dioxide in the air.

Gauge Pressure

Gauge pressure uses atmospheric pressure as a reference, and therefore will vary according to the barometric reading.


An amorphous solid which is often transparent.

A very clear and durable quartz glass can be made from pure silica which is very tough and resistant to thermal shock, being able to survive immersion in water while red hot. Glass will transmit, reflect and refract light; these qualities can be enhanced by cutting and polishing to make optical lenses, prisms, fine glassware, and optical fibers for high speed data transmission by light. When extruded as glass fiber and matted as glass wool it becomes a thermal insulating material, and when these glass fibers are embedded into an organic polymer plastic, they are a key structural reinforcement part of the composite material fiberglass.


A simple sugar-alcohol compound. It is a colorless, odorless, viscous liquid.

Glycerin is the most common fill fluid. Because of its unique fluid properties, Glycerin has become the standard for liquid filled gauges. Glycerine’s clarity, viscosity, stability, cost, solubility, low toxicity make Glycerine an ideal fluid for many applications. Mineral oils and silicone fluids are used when temperature extremes, chemical compatibility or viscosity fall outside of Glycerin use. Glycerin is not compatible with strong oxidizers such as oxygen, chlorine, hydrogen peroxide, or nitric acid. Glycerin & Silicone are explosive in contact with chlorine.


Gold’s high malleability, ductility, resistance to corrosion and conductivity of electricity have led to its continued use in corrosion resistant electrical connectors of all types.

The most important industrial use is in the fabrication of corrosion-free electrical connectors in electrical devices. Though gold is attacked by free chlorine, its good conductivity and general resistance to oxidation and corrosion in other environments has led to its widespread industrial use as a thin-layer coating on electrical connectors, thereby ensuring good connection. Besides sliding electrical contacts, gold is also used in electrical contacts because of its resistance to corrosion, electrical conductivity, ductility and lack of toxicity. Fine gold wires are used to connect semiconductor devices to their packages through a process known as wire bonding.


Refers to a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification (EASC), a regional standards organization operating under the auspices of the Commonwealth of Independent States (CIS). These are GOST-R, GOST-B, GOST-U and GOST-K certification trademarks demonstrating product compliance to Russia, Belarus, Ukraine, and Kazakhstan.


A crystalline form of carbon in its most stable form under standard conditions.

Graphite electrodes carry the electricity that melts scrap iron and steel in the majority of steel furnaces. Graphite is also used in carbon fiber reinforced plastics and in heat-resistant composites such as reinforced carbon-carbon (RCC). Modern smokeless powder is coated in graphite to prevent the buildup of static charge. Other uses include Batteries, steel making, brake lining, foundry facing and lubricants.


The reference point of an electrical system, a common return path for electric current, or alternatively, the local earth potential (earth ground).

Grounded Junction

A thermocouple construction where the junction is attached (grounded) to the sheath as contrasted to an ungrounded or exposed junction type.


Half-Duplex communications refers to communications that run one direction at a time.

Halocarbon Oil

Halocarbon oils, greases and waxes are polychlorotrifluoroethylenes (PCTFE), which are chemically inert and nonflammable lubricants with high thermal stability, good lubricity, high dielectric strength and low compressibility.

As an inert fill fluid it is compatible with chlorine. Halocarbon is explosive in contact with aluminum and magnesium.

Mechanical seals filled with Halocarbon oils are installed on equipment handling aggressive chemicals where the reaction between conventional barrier fluids and aggressive chemicals could be explosive.

HART Protocol

The HART Communications Protocol (Highway Addressable Remote Transducer Protocol) is an early implementation of Fieldbus, a digital industrial automation protocol. Its most notable advantage is that it can communicate over legacy 4-20 mA analog instrumentation wiring, sharing the pair of wires used by the older system.


The primary function of the Hastelloy super alloys is that of effective survival under high-temperature, high-stress service in a moderately to severely corrosive, and/or erosion-prone environment where more common and less expensive iron-based alloys would fail, including the pressure vessels of some nuclear reactors, chemical reactors, distillation equipment, and pipes and valves in chemical industry. Although a super alloy, Hastelloy does experience degradation due to fabricating and handling. Electropolishing or passivation of Hastelloy can improve corrosion resistance.

Hastelloy B-3

Hastelloy® B-3® alloy is an additional member of the nickel-molybdenum family of alloys with high resistance to hydrochloric acid at all concentrations and temperatures. It also withstands sulfuric, acetic, formic and phosphoric acids, and other nonoxidizing media. B-3 alloy has a special chemistry designed to achieve a level of thermal stability greatly superior to that of its predecessors, e.g. Hastelloy B-2 alloy. B-3 alloy has excellent resistance to pitting corrosion, to stress-corrosion cracking and to knife-line and heat-affected zone attack.

Hastelloy C

Hastelloy C is an alloy composed of nickel, molybdenum, chromium and iron.

Hastelloy™ Alloy-C maintains its outstanding properties in extreme heat, holding its strength and resisting oxidation. Hastelloy C is also resists chlorine and compounds with chlorine, as well as strong oxidizing acids, acid mixes and salts. One of the most corrosion-resistant alloys, it is exceptional in high-stress applications and in environments prone to repeated thermal shock.

Hastelloy C-2000

The nickel-chromium-molybdenum C-type alloys have a long history of use in the Chemical Process Industries and are known for their versatility. Not only do they resist all acids over large temperature ranges, but they also resist attacks induced by chlorides and other halide solutions, specifically pitting, crevice attack, and stress corrosion cracking. The technical objective during the design of Hastelloy® C-2000® alloy was even greater versatility, as compared with the traditional Ni-Cr-Mo alloys. This was accomplished by use of a high chromium content (23 wt.%), a high molybdenum content (16 wt.%), and a small but effective addition of copper (1.6 wt.%). The copper was found to provide enhanced temperature capability in sulfuric acid, hydrofluoric acid, and dilute hydrochloric acid.

Hastelloy C-22

Hastelloy® C-22® alloy is a versatile nickel-chromium- molybdenum-tungsten alloy with better overall corrosion resistance than other Ni-Cr-Mo alloys, including Hastelloy C-276 and C-4 alloys and alloy 625.

C-22 alloy has outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking. It has excellent resistance to oxidizing aqueous media including wet chlorine and mixtures containing nitric acid or oxidizing acids with chloride ions. Also, C-22 alloy offers optimum resistance to environments where reducing and oxidizing conditions are encountered in process streams. Because of such versatility it can be used where “upset” conditions are likely to occur or in multi-purpose plants. C-22 alloy has exceptional resistance to a wide variety of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, chlorine, hot contaminated solutions (organic and inorganic), formic and acetic acids, acetic anhydride, and seawater and brine solutions. C-22 alloy resists the formation of grain-boundary precipitates in the weld heat-affected zone, thus making it suitable for most chemical process applications in the as-welded condition.

Hastelloy C-22HS

Hastelloy® C-22HSTM alloy is corrosion-resistant, nickel-chromium-molybdenum alloy which can be heat treated to obtain a strength approximately double that of other C-type alloys.

Importantly, the corrosion resistance and ductility of the alloy remain excellent when in the high strength condition. In addition to its high uniform corrosion resistance in oxidizing as well as reducing environments, the as-heat treated C-22HS alloy possesses high resistance to chloride-induced pitting and crevice corrosion attack.

Hastelloy C-276

Hastelloy® C-276 alloy is a nickel-molybdenum-chromium wrought alloy that is generally considered a versatile corrosion-resistance alloy.

This alloy resists the formation of grain-boundary precipitaties in the weld heat-affected zone, thus making it suitable for most chemical process applications in the as-welded condition. Hastelloy C-276 alloy has excellent resistance to a wide variety of chemical process environments, including strong oxidizers such as ferric and cupric chlorides, hot contaminated media (organic and inorganic), chlorine, formic and acetic acids, acetic anhydride, and seawater and brine solutions.

It is used in flue gas desulfurization systems because of its excellent resistance to sulfur compounds and chloride ions encounted in most scrubbers. C-276 alloy has excellent resistance to localized corrosion and to both oxidizing and reducing media and as well as pitting and to stress-corrosion cracking. It is also one of the few materials that withstands the corrosive effects of wet chlorine gas, hypochlorite, and chlorine dioxide.

Because of its versatility, C-276 alloy can be used where "upset" conditions are likely to occur or in multipurpose plants.

Hastelloy C-4

Hastelloy C-4 alloy is a nickel-chromium-molybdenum alloy with high-temperature stability as evidenced by high ductility and corrosion resistance even after aging in the 1200 to 1900°F (649 to 1038°C) range. This alloy resists the formation of grain-boundary precipitates in the weld heat-affected zone, this making it suitable for most chemical process applications in the as-welded condition. C-4 alloy also has excellent resistance to stress-corrosion cracking and to oxidizing atmospheres up to 1900°F (1038°C). Hastelloy C-4 alloy has exceptional resistance to a wide variety of chemical process environments. These include hot contaminated mineral acids, solvents, chlorine and chlorine contaminated media (organic and inorganic), dry chlorine, formic and acetic acids, acetic anhydride, and seawater and brine solutions.

Hastelloy G-30

Hastelloy® G-30® alloy is a high chromium nickel-base alloy which shows superior corrosion resistance over most other nickel and iron-base alloys in commercial phosphoric acids as well as many complex environments containing highly oxidizing acids such as nitric/hydrochloric , nitric/hydrofluoric and sulfuric acids. The resistance of G-30 alloy to the formation of grain boundary precipitates in the heat-affected zone makes it suitable for use in most chemical process applications in the as-welded condition.

Hastelloy G-35

Hastelloy® G-35® alloy was designed to resist “wet process” phosphoric acid, which is widely used in the production of fertilizers. It was also designed to resist localized attack in the presence of chlorides, since under-deposit attack is a potential problem in evaporators used to concentrate “wet process” phosphoric acid. As a result of its high-chromium content, G-35 alloy is highly resistant to other oxidizing acids. It possesses moderate resistance to reducing acids, as a result of its appreciable molybdenum content, and, unlike other nickel-chromium-molybdenum alloys, it is very resistant to “caustic dealloying” in hot sodium hydroxide. Finally, G-35 alloy is much less susceptible to chloride-induced stress corrosion cracking than the high-chromium stainless steels and nickel-chromium-iron alloys traditionally used in “wet process” phosphoric acid.

Hastelloy Hybrid-BC1

Hastelloy® Hybrid-BC1® alloy possesses a higher resistance to hydrochloric and sulfuric acids than the nickel-chromium-molybdenum (C-type) alloys, and can tolerate the presence of oxidizing species. The alloy also exhibits high resistance to pitting and crevice corrosion. Hybrid-BC1 alloy excels in reducing acids and acid mixtures (with or without halides) open to oxygen and other oxidizing residuals/contaminants.

Hazardous Location

Defined as an area in which flammable or combustible mixtures are present.

Hermetic Seal

A method of sealing the electrical switching element in a sensor so that it is unaffected by all ambient external corrosive agents and explosive gases. Sealing must be accomplished by soldering, brazing, welding, and glass to metal fusion.


A topic dealing with the mechanical properties of liquids or fluids. At a very basic level, hydraulics is the liquid version of pneumatics. Fluid mechanics provides the theoretical foundation for hydraulics, which focuses on the engineering uses of fluid properties. In fluid power, hydraulics are used for the generation, control, and transmission of power by the use of pressurized liquids. Hydraulic topics cover concepts such as pipe flow, dam design, fluidics and fluid control circuitry, pumps, turbines, hydropower, computational fluid dynamics, flow measurement, river channel behavior and erosion.


Deviation in output within the transducer range when first approaching this point with increasing pressure and then with decreasing pressure.


The International Electrotechnical Commission's set of standards for non-explosive atmospheres. The IEC cooperates closely with the International Organization for Standardization (ISO) and the International Telecommunication Union (ITU). IEC standards cover a vast range of technologies from power generation, transmission and distribution to home appliances and office equipment, semiconductors, fibre optics, batteries, solar energy, nanotechnology and marine energy as well as many others.

The IEC also manages three global conformity assessment systems that certify whether equipment, system or components conform to its International Standards. The IEC charter embraces all electrotechnologies including energy production and distribution, electronics, magnetics and electromagnetics, electroacoustics, multimedia, telecommunication and medical technology, as well as associated general disciplines such as terminology and symbols, electromagnetic compatibility (by its Advisory Committee on Electromagnetic Compatibility, ACEC), measurement and performance, dependability, design and development, safety and the environment.


International Electrotechnical Commission System for Certification to Standards relating to equipment for use in explosive atmospheres (IECEx System). IECEx Certified Service Facilities Scheme Assesses and certifies that organizations and workshops that provide repair and overhaul services to the Ex industry do so respecting the strict requirement of IEC International Standard 60079-19.


The total opposition of a circuit to the flow of alternating current.

It includes resistance and reactance, and is measured in ohms.


A family of austenite nickel-chromium-based superalloys.

Inconel alloys are oxidation and corrosion resistant materials well suited for service in extreme environments subjected to pressure and heat. When heated, Inconel forms a thick, stable, passivating oxide layer protecting the surface from further attack. Inconel retains strength over a wide temperature range, attractive for high temperature applications where aluminum and steel would succumb to creep as a result of thermally induced crystal vacancies.

Inconel alloys are typically used in high temperature applications.


A device which monitors and displays the condition of a process variable without exerting any control action. Indicators may be equipped with alarms or other auxiliary outputs


The property of an electrical conductor by which a change in current flowing through it induces an electromotive force in both the conductor itself and in any nearby conductors by mutual inductance.

Inductive Technology

Technology based on inductance, the property of an electric circuit by which an electromotive force is induced in it by a variation of current, either

1) in the circuit itself, or

2) in a neighboring circuit.


The National Institute of Metrology, Standardization and Industrial Quality (INMETRO) is a Brazilian federal autarchy, linked to MDIC, the Ministry of Development, Industry and Foreign Commerce. In Brazil, certification bodies must be accredited by INMETRO. Electrical and electronic products that meet Brazilian requirements and that are certified by an INMETRO accredited organization must carry the mandatory INMETRO mark along with the mark of the certification organization, such as UCIEE.

Input and Output Resistance

The resistance measured across the input (excitation) and output (signal) terminals of an unamplified transducer.

Input Fail Safe

Direction in which signal is driven in the event of a sensor failure. Upscale will drive the signal fully upscale, and downscale will drive the signal fully downscale. The control output will respond as if the sensor has not failed.

Input Impedance

The impedance from the source into the network being connected. In other words, the input impedance is the impedance, if placed across the input terminals, that would produce the same voltage across and current through the input terminals as the electrical network being connected. Therefore, the input impedance of the network being connected and the output impedance of the source determines the transfer function from the source to the input terminals of the circuit.

Input Resistance

DC (or AC) resistance measured across the input terminals with signal leads disconnected.

Insulation Resistance

The resistance measured between specified insulated portions of a transducer when a specific DC voltage is applied at room conditions.


PID parameter (also called reset) which monitors and corrects the error signal between the setpoint and the process variable.


A common boundary between electronic systems, or parts of a single system.

Interface Module

DIN rail or panel mounted printed circuit board modules that give design flexibility, simplify panel layouts, and reduce maintenance and downtime.

Intrinsically Safe

An instrument which will not produce any spark or thermal effect, under normal or abnormal conditions, that will ignite a specified gas mixture.


European environmental ratings similar to USA NEMA ratings.

Iron Vane

A technique for measuring AC or DC current using mutual repulsion of magnetic fields. The rotation is proportional to the strength of the fields, which is proportional to the current flowing in the field coil.

Also described as 'moving vane', 'moving iron' or 'repulsion'.

IS Rating

A rating administered by the ISCA that evaluates sustainability across the design, construction and operation of infrastructure. The Infrastructure Sustainability Council of Australia (ISCA) is the peak industry body for advancing sustainability in Australia’s infrastructure. ISCA is a member-based, not-for-profit industry (public and private) council.

ISCA developed and administers the Infrastructure Sustainability (IS) rating scheme. IS is Australia’s only comprehensive rating system for evaluating sustainability across design, construction and operation of infrastructure. IS evaluates the sustainability (including environmental, social, economic and governance aspects) of infrastructure projects and assets.


The International Organization for Standardization, a worldwide federation of national standards bodies from some 140 countries. Equivalent to ASTM.

ISO 9000

Family of standards concerned with "quality management". This means what the organization does to enhance customer satisfaction by meeting customer and applicable regulatory requirements.

ISO Metric Screw Thread

The ISO metric screw thread is the most common type of general-purpose screw thread used worldwide. The "M" designation for metric screws indicates the nominal outer diameter of the screw, in millimeters (e.g. an M6 screw has a nominal outer diameter of 6 millimeters).


A process or area that is a constant temperature.


The situation where properties are independent of the direction in which they are measured.


International Temperature Scale, Revised 1990. The currently accepted thermodynamic temperature scale. Replace the previous standard IPTS-68.


Wire links that allow for changes to be made in input and output hardware configurations.


The point in a thermocouple where the two dissimilar metals are joined.

Junction Box

A container for electrical connections, usually intended to conceal them from sight and deter tampering. A small metal or plastic junction box may form part of an electrical conduit or thermoplastic-sheathed cable (TPS) wiring system in a building.

Knife-Edge Pointer

Analog meter pointer with a flattened end that is turned edgewise so that the thinnest dimension or edge is seen by the observer. Often used with mirror-backed scale for increased reading accuracy by elimination of parallax.

Krytox Oil

Krytox™ oils offer a combination of properties that provide exceptional performance to help solve challenging lubrication problems.

Krytox™ oils combine high-temperature performance, non-flammability, and chemical inertness under a wide range of conditions. Krytox™ oils offer high stability, lubricity and viscosity. It is thermally stable and insoluble in water, acids, bases, and most organic solvents. It is nonvolatile and useful over a broad temperature range of −75 to 350 °C (−100 to 660 °F) or higher. Its high resistance to ionizing radiation makes it useful for the aerospace and nuclear industries. It can also withstand extreme pressure and high mechanical stress.

Laminated Glass

A type of safety glass that holds together when shattered. In the event of breaking, it is held in place by an interlayer, typically of polyvinyl butyral (PVB) or ethylene-vinyl acetate (EVA), between its two or more layers of glass. The interlayer keeps the layers of glass bonded even when broken, and its high strength prevents the glass from breaking up into large sharp pieces. This produces a characteristic "spider web" cracking pattern when the impact is not enough to completely pierce the glass. Laminated glass is normally used when there is a possibility of human impact or where the glass could fall if shattered and also for architectural applications.


A condition that requires the manual reset of a tripped relay. The tripped relay cannot be reset (re-energized) until the indicating pointer or display is in a non-alarm position.

Lead Compensation

Technique for minimizing or eliminating errors due to signal leads.


Flow of gas or fluid past a seat or seal, in the closed position.

Least Significant Digit

The rightmost active digit of a digital display.

Level Switch

These devices equip electrodes to detect liquid levels.

They have been widely used in water works and sewers for buildings and housing complexes, industrial facilities and equipment, water treatment plants and sewage treatment facilities, and many other applications.

Limp Diaphragm

An elastomer or plastic diaphragm which is used in a device. This type of diaphragm conforms to the shape of the sensing pressure plate and has no rigid structure itself.

Line Rejection

Insensitivity to a power line frequency interference signal.

Usually expressed in dB.


The maximum deviation of the transducer output from a defined straight line during increasing pressure in a calibration cycle.

Linearity (End Point or Terminal)

Linearity as referring to a straight line between end points.

Linearity Error

A measure of the departure from a straight-line response in the relationship between two quantities, where the change in one quantity is directly proportional to a change in the other quantity.

Usually expressed as a maximum percent.

Lloyd's Register

Lloyd's Register Group Limited (LR) is a technical and business services organisation and a maritime classification society, wholly owned by the Lloyd’s Register Foundation, a UK charity dedicated to research and education in science and engineering. Since 1760, its stated aims are to enhance the safety of life, property, and the environment, by helping its clients (including by validation, certification and accreditation) to ensure the quality construction, and operation, of critical infrastructure. Historically, as Lloyd's Register of Shipping, it was a specifically maritime organisation. During the late 20th century, it diversified into other industries including oil and gas, process industries, nuclear, and rail. Through its 100% subsidiary Lloyd's Register Quality Assurance Ltd (LRQA), it is also a major vendor of independent assessment services, including management systems certification for quality certification to ISO9001, ISO14001 and OSHAS18001.

Loop Gain

The product of the gains of all the elements in a loop.

Lower Range Limit

The lowest value of the measured variable that the analog output of the transmitter is capable of measuring.

Lower Range Limit, LRL, is factory set and not modifiable by the user.


The Low Voltage Directive is one of the oldest Single Market Directives adopted by the European Union before the "New" or "Global" Approach. The Directive provides common broad objectives for safety regulations, so that electrical equipment approved by any EU member country will be acceptable for use in all other EU countries. The Low Voltage Directive does not supply any specific technical standards that must be met, instead relying on IEC technical standards to guide designers to produce safe products. Products that conform to the general principles of the Low Voltage Directive and the relevant particular safety standards are marked with the CE marking to indicate compliance and acceptance throughout the EU. Conformance is asserted by the manufacturer based on its conformity assessment.

The directive covers electrical equipment with a voltage at input or output terminals between 50 and 1000 volts for alternating current (AC) or between 75 and 1500 volts for direct current (DC). Importantly, it does not cover voltages within equipment. The directive does not cover components (broadly, this refers to individual electronic components).

Certain classes of equipment, covered by other technical standards, are listed in Annex III of the Directive as excluded from its scope. These items include medical devices, electricity meters, railway or maritime equipment, and electrical plugs and sockets for domestic use.


The communication device which controls the operation of slave devices in a communications environment. In a Master-Slave operation, the Slave device can only respond when requested by the Master device.

Maximum Diaphragm Temperature

The maximum temperature of the process media to which the transducer tip below the mounting threads can be exposed. Maximum strain gage temperature is the maximum environmental temperature at which the strain gage housing should be exposed.

Maximum Pressure

Pressure that may be applied to a transducer without changing the transducer`s performance beyond specified tolerances.


Physical quantity, property or condition which is measured. The term measurand is preferred to "input", "parameter to be measured", "physical phenomenon", "stimulus", and/or "variable."

Measuring Junction

That junction of a thermocouple subjected to the temperature to be measured.

Mirror Scale

An analog meter scale with a mirror arc that enables alignment of the eye's line of sight perpendicular to the scale when taking a reading. Eliminates parallax, considerably improves reading accuracy.


Monel is a group of nickel alloys, primarily composed of nickel and copper, with small amounts of iron, manganese, carbon, and silicon.

Stronger than pure nickel, Monel alloys are resistant to corrosion by many agents, including rapidly flowing seawater. It also has good ductility and thermal conductivity.

Monel typically finds application in marine engineering, chemical and hydro-carbon processings, heat exchangers, valves and pumps.

Mounting Error

The error resultant from installing the pressure transducer, both electrical and mechanical.


Component used to protect electronic circuitry from voltage transients.


A mode of operation for HART transmitters. Establishes a communication system where more than two devices are connected together on a single transmission line. In such system, each device must have a unique address.

The HART protocol can be operated in multidrop mode, with up to 15 slave devices on one pair of wires. The analog (4-20 mA) signals cannot be used in this mode since they would simply add together in this mode. With HART multidrop mode, each slave device assumes a fixed output current value of 4 mA.


A technique which allows different input (or output) signals to use the same lines at different times, controlled by an external signal. Multiplexing is used to save on wiring and I/O ports.


Nonprofit technical association that develops and maintains standards that deal exclusively with protection and performance of materials in corrosive environments. The membership represents a cross–section of industry concerned with corrosion prevention and control.


The American national standard that contains provisions considered necessary for safeguarding persons and property from hazards arising from the use of electricity. Generally, the code covers electric conductors and equipment installed within or on public and private buildings or other structures.

Needle Valve

A type of valve having a small port and a threaded, needle-shaped plunger. It allows precise regulation of flow, although it is generally only capable of relatively low flow rates.


A voluntary organization that adopts standards for electrical equipment. NEMA standards are designed to eliminate misunderstandings between the manufacturer and the purchaser and to assist the purchaser in selecting and obtaining the proper product for a particular need.

NEMA ratings are often directly convertible to IP (Ingress Protection) ratings, so we often write these two ratings together.


Norges Elektriske Materiellkontroll (NEMKO) is a Norwegian private organization that supervises safety testing for electrical equipment manufacturing. The Nemko Group offers testing, inspection and certification services concerning products, machinery, installations and systems worldwide.


A family of synthetic rubbers that are produced by polymerization of chloroprene.

Neoprene exhibits good chemical stability and maintains flexibility over a wide temperature range.

It is used in a wide variety of applications such as electrical insulation, liquid and sheet applied elastomeric membranes or flashings, and automotive fan belts.


National Supervision and Inspection Center for Explosion Protection and Safety of Instrumentation (NEPSI) is an establishment engaged in the development of explosion protection technology and the testing, verification and certification of electrical equipment for use in explosive atmospheres.

NEPSI is an international testing laboratory accredited by IECEx.

Newtonian Fluids

Fluids which exhibit constant viscosities independent of the shear rate. Water, glycerin, oil and other small molecule fluids are Newtonian.

NFPA (National Fire Protection Association)

An organization that promotes the science and improves methods of fire protection. NFPA codes, standards, and recommended practices are intended to prescribe reasonable measures for minimizing losses of life and property by fire. NFPA sponsors the National Electrical Code under auspices of the American National Standards Institute.

NFPA (National Fluid Power Association)

A nonprofit national trade association that coordinates and develops voluntary standards for manufacturers of hydraulic and pneumatic systems and components.

Nimonic Alloy 105

Nimonic is a registered trademark of Special Metals Corporation that refers to a family of nickel-based high-temperature low creep superalloys.

Nimonic alloys typically consist of more than 50% nickel and 20% chromium with additives such as titanium and aluminium.

The main use is in gas turbine components and extremely high performance reciprocating internal combustion engines.


The National Institute of Standards and Technology (formerly NBS) is a measurement standards laboratory which is a non-regulatory agency of the United States Department of Commerce. The institute's official mission is to promote U.S. innovation and industrial competitiveness by advancing measurement science, standards, and technology in ways that enhance economic security and improve our quality of life. NIST publishes the Handbook 44 that provides the "Specifications, tolerances, and other technical requirements for weighing and measuring devices".

Nitrile Rubber

A synthetic rubber copolymer of acrylonitrile (ACN) and butadiene.

Although its physical and chemical properties vary depending on the polymer’s composition of nitrile, this form of synthetic rubber is unusual in being resistant to oil, fuel, and other chemicals. It is used in the automotive and aeronautical industry to make fuel and oil handling hoses, seals, grommets, and self-sealing fuel tanks, since ordinary rubbers cannot be used. Buna-N's ability to withstand a range of temperatures from −40 to 108 °C (−40 to 226 °F) makes it an ideal material for aeronautical applications. Nitrile rubber is more resistant than natural rubber to oils and acids: it has superior strength but inferior flexibility. Nitrile rubber is generally resistant to aliphatic hydrocarbons. Nitrile, like natural rubber, can be attacked by ozone, ketones, esters and aldehydes.

No Bleed-No Relief Diaphragm

A diaphragm assembly that does not allow process medium to exit through the diaphragm.


An unwanted signal which can contribute to errors in measurement. Examples are hum (power lines), radio frequency interference (RFI), electromagnetic interference (EMI), and broadband or white noise.

Nominal Range

The maximum distance that this sensor can detect is defined "nominal range". Some sensors have adjustments of the nominal range or means to report a graduated detection distance.

Non Hazardous Location

Defined as an area in which flammable or combustible mixtures are not present.


In an ideal system, the input-out relationship is linear (i.e., straight line). Any departure from straight line is expressed as non-linearity. Two methods are used for measurement. The "best straight line" approach compromises the end points and situates the line to give the most optimistic answer.

Non-Newtionial Fluids

Fluids having viscosities that depend on the shear rate. Polymer solutions and melts are non-Newtonian fluids. They also exhibit other non-Newtonian properties such as stress relaxation and normal stresses.

Normally Closed

The state of a switching device (relay or SSR) whose non-powered state is connected.

Normally Open

The state of a switching device (relay or SSR) whose non-powered state provides no connection.

Normal-Mode Rejection

The ability of a meter to filter out noise that appears across the signal inputs in the same manner as the desired signal.

Also known as series mode rejection.

NPT Connections

NPT (National Pipe Thread) seals are the most popular type of seal for pressure calibration systems in the U.S. and Canada. NPT male (MNPT) adapters have a taper thread that wedges into the female NPT (FNPT) adapter.

They seal due to the “out of roundness principle” which means that the male stretches the female fitting until there is so much force that the connection can hold pressure. One of the challenges with this design is that if you connect stainless steel to stainless steel then over-tightening or poor lubrication can cause gauling and damage to the threads. Thread sealant is needed to seal but only 2 turns of thread sealant is required. Any more than that and the seal can leak around the thread sealant.

Off-Line Configuration

Those procedures and data exchanges which do not have a direct impact upon the Analog Signal which the transmitter outputs or reports and which do not effect the measurement data transmitted digitally by the transmitter. They typically refer to operations which can be performed on a transmitter on a bench with the transmitter removed from a process control system.


The non-zero output of a device for zero input.

Offset Current

The difference between two bias currents drawn by the inputs of a differential amplifier.

On-Line Configuration

Any operation which is performed on a transmitter which characterizes the response of the transmitter or which modifies its configuration parameters, values, or settings.

On-Off Control

Non-proportional control in which the controlled process input is either fully ON or fully OFF depending on whether the temperature is above or below the control point dead-band.

Operating Temperature

The temperature rating of the device considering both media and ambient temperature extremes. Factors that affect this rating include distance between media and wetted parts as well as installation methods.


An isolation device that provides an electrical barrier between related circuits.


A mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, creating a seal at the interface.

The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. O-rings are one of the most common seals used in machine design because they are inexpensive, easy to make, reliable, and have simple mounting requirements. They can seal tens of megapascals (thousands of psi) of pressure.


The electrical signal, which is produced by a pressure applied to the transducer sensor.

Output Impedance

The opposition exhibited by its output terminals to an alternating current (AC) of a particular frequency as a result of resistance, inductance and capacitance. The small-signal impedance at DC (frequency of 0) is the same as the resistive component of the impedance and is termed output resistance.


The excess load beyond full-scale value that an instrument can withstand without damage or failure.

Expressed as a percent of a full-scale value.


The maximum specified pressure which may be applied to the sensing element of a sensor without causing a permanent change in the output characteristics.


A reading that exceeds full scale.


The amount by which a meter or process exceeds the final value during a transition.

Usually expressed as percent of amplitude for a step change.


The Stahlpanzerrohrgewinde standard for screw threads is a technical standard created in Germany. The German name translates to English as 'steel conduit thread'. The thread is used to join pieces of electrical conduit and cable glands.

Panzergewinde sizes are named with the prefix PG plus a nominal number which approximately corresponds to the maximum cable diameter (in millimeters) that can be passed through the conduit.

Because the walls of the conduit are usually relatively thin, the thread depth should not be very large. The Verband der Elektrotechnik, Elektronik und Informationstechnik (VDE) originally standardized the thread for use with conduit and cable glands that were made of steel, although today the thread is used with both steel and polyvinyl chloride (PVC).

Beginning in 2000, the VDE standard for cable glands (VDE 0619) was formally replaced by EN 50262. After a transitional period of several years during which it could still be used, it was replaced in 2003 by a final metric fine thread with 1.5 mm (0.0591 in) pitch. Similarly, conduit threads were replaced by EN 60423.

Even today, Panzergewinde cable glands are still found on chemical reactors and bioreactors (for example, PG13.5 thread for screwing in sensors) and various other equipment, enclosures, junction boxes, and connectors.


Parallel communications provides a multipath avenue for the transmission of several, often as many as 8 bits, bits simultaneously. Serial communications is the transmission of digital information from one device to another on a single transmission path one bit at a time. The HART protocol uses serial asynchronous communications.


Parity refers to the appending of an additional bit to a byte of information for the purposes of error detection.

Parity can be ODD or EVEN by agreement between the communicating parties. For ODD parity the extra bit is a 1 or a 0, so as to make the total of the ones in the byte add up to an odd number. For EVEN parity the total would add up to an even number. HART protocol appends an ODD parity bit to each byte transmitted.

Partial Stroke Test

Partial stroke testing (or PST) is a technique used in a control system to allow the user to test a percentage of the possible failure modes of a shut down valve without the need to physically close the valve. PST is used to assist in determining that the safety function will operate on demand.


A thermoplastic engineering polymer that is used as an insulator in the electrical and electronics industries. It is a thermoplastic semi-crystalline polymer, and a type of polyester.

PBT is resistant to solvents, shrinks very little during forming, is mechanically strong, heat-resistant up to 150 °C, and can be treated with flame retardants to make it noncombustible. PBT is closely related to other thermoplastic polyesters. Compared to PET (polyethylene terephthalate), PBT has slightly lower strength and rigidity, slightly better impact resistance, and a slightly lower glass transition temperature. PBT and PET are sensitive to hot water above 60 °C (140 °F). PBT and PET need UV protection if used outdoors, and most grades of these polyesters are flammable, although additives can be used to improve both UV and flammability properties.


Polychlorotrifluoroethene (PCTFE or PTFCE) is a thermoplastic chlorofluoropolymer.

It has the lowest water vapor transmission rate of any plastic. PCTFE has high tensile strength and good thermal characteristics. It is non-flammable and heat resistant. It has a low coefficient of thermal expansion. It has good chemical resistance. It does not absorb visible light. When subjected to high energy radiations, like PTFE, it undergoes degradation. PCTFE is resistant to the attack by most chemicals and oxidizing agents; a property which is exhibited due to the presence of high fluorine content. PCTFE is resistant to oxidation because it does not have any hydrogen atoms.

PCTFE is used for laminating polymers like PVC, polypropylene, PETG and APET. It is also used in tubes, valves, chemical tank liners, O-rings, seals and gaskets. Low molecular weight PCTFE waxes, oils and greases find their application as inert sealants and lubricants. PCTFE is used to protect sensitive electronic components because of its excellent electrical resistance and water repulsion. Other uses include flexible printed circuits and insulation of wires and cables.

Peak Hold

An instrument function that permits retaining and displaying the peak value momentarily reached by a signal.


Refers to the Pressure Equipment Directive of the EU. PED sets out the standards for the design and fabrication of pressure equipment (steam boilers, pressure vessels, piping, safety valves etc...). It also sets the administrative procedures requirements for the conformity assessment of pressure equipment. It has been mandatory throughout the EU since 30 May 2002. This is enacted in the UK as the Pressure Equipment Regulations (PER). The standards and regulations regarding pressure vessels and boiler safety are similar to the US standards defined by the American Society of Mechanical Engineers (ASME). This enables most international inspection agencies to provide both verification and certification services to assess compliance to the different pressure equipment directives.


Polyether ether ketone (PEEK) is a colourless organic thermoplastic polymer in the polyaryletherketone (PAEK) family, used in engineering applications.

PEEK is a semi-crystalline thermoplastic with excellent mechanical and chemical resistance properties that are retained to high temperatures. It is highly resistant to thermal degradation as well as attack by both organic and aqueous environments.

Because of its robustness, PEEK is used to fabricate items used in demanding applications, including bearings, piston parts, pumps, HPLC columns, compressor plate valves, and cable insulation. It is one of the few plastics compatible with ultra-high vacuum applications. It is extensively used in the aerospace, automotive, and chemical process industries.


Compound containing an even higher amount of fluoride than FKM.

They have further improved resistance to high temperatures and chemicals and even withstand environments where Oxygen-Plasma are present for many hours. Certain grades have a maximum continuous service temperature of 327 °C (621 °F).

They are commonly used to make O-rings and gaskets that are used in applications that involve contact with hydrocarbons or highly corrosive fluids, or when a wide range of temperatures is encountered.


The most common thermoplastic polymer resin of the polyester family.

They withstand both freezing and oven baking temperatures. Its properties include high tensile strength, high resistance to stretching, both wet and dry, and good resistance to degradation by chemical bleaches and to abrasion. Because of its high mechanical strength, PET film is often used in tape applications, such as the carrier for magnetic tape or backing for pressure-sensitive adhesive tapes. When filled with glass particles or fibres, it becomes significantly stiffer and more durable (used for engineering resins in that form).

PET is commonly recycled, and has the number 1 as its recycling symbol.

Phase Angle

The difference in electrical degrees by which current leads voltage in an inductive circuit or lags voltage in a capacitive circuit. Also the phase displacement between primary and secondary currents in a current transformer.

Phenolic Plastic

A Synthetic polymer obtained by the reaction of phenol with formaldehyde.

Phenol formaldehyde resins are known for the production of molded products and as coatings and adhesives. Phenolic laminates are made by impregnating one or more layers of a base material such as paper, fiberglass or cotton with phenolic resin and laminating the resin-saturated base material under heat and pressure. The base material choice depends on the intended application of the finished product.

Paper phenolics are used in manufacturing electrical components such as punch-through boards and household laminates. Glass phenolics are particularly well suited for use in the high speed bearing market. Phenolic micro-balloons are used for density control. Sometimes people select phenolic resin parts because their coefficient of thermal expansion closely matches that of the aluminum used for other parts of a system.

Phosphate Conversion Coating

Phosphate coatings are used on steel parts for corrosion resistance, lubricity, or as a foundation for subsequent coatings or painting. Phosphate conversion coatings can also be used on aluminium, zinc, cadmium, silver and tin.

Phosphate coatings are often used to provide corrosion resistance, however, phosphate coatings on their own do not provide this because the coating is porous. Therefore, oil or other sealers are used to achieve corrosion resistance. Most phosphate coatings serve as a surface preparation for further coating and/or painting, a function it performs effectively with excellent adhesion and electric isolation. The porosity allows the additional materials to seep into the phosphate coating and become mechanically interlocked after drying. The dielectric nature will electrically isolate anodic and cathodic areas on the surface of the part, minimizing underfilm corrosion that sometimes occurs at the interface of the paint/coating and the substrate.

Phosphor bronze

An alloy of copper and tin with a significant phosphorus content.

These alloys are notable for their toughness, strength, low coefficient of friction, and fine grain. The phosphorus also improves the fluidity of the molten metal and thereby improves the castability, and improves mechanical properties by cleaning up the grain boundaries. The phosphorous increases the wear resistance and stiffness of the alloy. The phosphor bronzes have superb spring qualities, high fatigue resistance, excellent formability and solderability, and high corrosion resistance.

They are primarily used for electrical products, other uses include corrosion resistant bellows, diaphragms, and spring washers. Leaded phosphor bronzes combine good strength and fatigue resistance with good machinability, high wear resistance and corrosion resistance.

PID Controller

The control algorithm providing proportional control with automatic Integral and Derivative terms. Mathematically determines the control action to be performed.


A change in resistance in a semiconductor, caused by an applied stress to the diaphragm.

Pivot and Jewel

Method of suspending the moving coil or moving iron vane in a magnetic field, in analog meters. The movable element is equipped with two metal pivots which engage glass or synthetic-jewel cup bearings.


A branch of physics applied to technology that makes use of gas or pressurized air. Pneumatic systems used extensively in industry are commonly powered by compressed air or compressed inert gases. A centrally located and electrically powered compressor powers cylinders, air motors, and other pneumatic devices. A pneumatic system controlled through manual or automatic solenoid valves is selected when it provides a lower cost, more flexible, or safer alternative to electric motors and actuators. Pneumatics also has applications in, construction and mining.


In electricity, the quality of having two oppositely charged poles, one positive and one negative.


A group of thermoplastic polymers containing carbonate groups in their chemical structures.

They are easily works, molded, and thermoformed. It is also good electrical insulator and have heat-resistant and flame-retardant properties. Polycarbonates used in engineering are strong, tough materials, and some grades are optically transparent. Polycarbonate is mainly used for electronic applications that capitalize on its collective safety features. It is also used in various products associated with electrical and telecommunications hardware.


A polymeric film possessing a unique combination of physical and mechanical properties which include long life, excellent deformation/set resistance, high resistance to temperature extremes, good tensile strength, and outstanding resistance to organic compounds. Polyimide materials are lightweight, flexible, resistant to heat and chemicals.

Therefore, they are used in the electronics industry for flexible cables, as an insulating film on magnet wire and for medical tubing.

The semiconductor industry uses polyimide as a high-temperature adhesive; it is also used as a mechanical stress buffer. The polyimide layers have good mechanical elongation and tensile strength, which also helps the adhesion between the polyimide layers or between polyimide layer and deposited metal layer. The minimum interaction between the gold film and the polyimide film, coupled with high temperature stability of the polyimide film, results in a system that provides reliable insulation when subjected to various types of environmental stresses. In coal-fired power plants, waste incinerators or cement plants, polyimide fibres are used to filter hot gases. In this application, a polyimide needle felt separates dust and particulate matter from the exhaust gas. Polyimide is not recommended for water service above 140 °F (60 °C).

Polyphenyle Sulfide

PPS is one of the most important high temperature thermoplastic polymers because it exhibits a number of desirable properties. These properties include resistance to heat, acids and alkalies, and to mildew, to bleaches, aging, sunlight, and abrasion. It absorbs only small amounts of solvents and resists dyeing.


A polymer composed of a chain of organic units joined by carbamate links. Polyurethane sealants are used to fill gaps thereby preventing air and water leakage. They are also used in conjunction with inorganic insulation, such as rockwool or ceramic fibres, for fire-stopping. Often electronic components are protected from environmental influence and mechanical shock by enclosing them in polyurethane. Typically polyurethanes are selected for the excellent abrasion resistances, good electrical properties, excellent adhesion, impact strength, and low-temperature flexibility. The disadvantage of polyurethanes is the limited upper service temperature. Often electronic components are protected from environmental influence and mechanical shock by enclosing them in polyurethane.

Poppet Valve

A valve typically used to control the timing and quantity of gas or vapour flow into an engine. It consists of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The portion of the hole where the plug meets with it is referred as the 'seat' or 'valve seat'. The shaft guides the plug portion by sliding through a valve guide. In exhaust applications a pressure differential helps to seal the valve and in intake valves a pressure differential helps open it.

Potential EMF

The relative voltage at a point in a circuit or in space with respect to some reference point.


A variable resistor often used to control a circuit.

Powder Coating

A type of coating that is applied as a free-flowing, dry powder.

The main difference between a conventional liquid paint and a powder coating is that the powder coating does not require a solvent to keep the binder and filler parts in a liquid suspension form. The coating is typically applied electrostatically and is then cured under heat to allow it to flow and form a "skin". The powder may be a thermoplastic or a thermoset polymer. It is usually used to create a hard finish that is tougher than conventional paint.

Powder coating is mainly used for coating of metals, such as household appliances or aluminium extrusions. There are two main categories of powder coating: thermosets and thermoplastics. The thermosetting variety incorporates a cross-linker into the formulation. When the powder is baked, it reacts with other chemical groups in the powder to polymerize, improving the performance properties. The thermoplastic variety does not undergo any additional actions during the baking process, but rather only flows out into the final coating.

Power Factor

The ratio of consumed power to apparent (volt-ampere) power in an AC circuit.

Power Supply

A separate unit or part of a circuit that supplies power to the rest of the circuit or to a system.


A factory set pressure switch available from stock, set to a predetermined set point.

Pressure Sensing Element

The portion of the pressure switch that is in contact with and moves as a result of a change in pressure / force.

The most common type of sensing elements are diaphragms, accordion bourdon tubes and pistons.

Pressure Switch

A pressure switch is an electrical mechanical device that converts pressure into motion to operate an electrical switching element.

Process Fluid

A pressurized gas or liquid that actuates a machine. Examples include steam in a steam engine, air in a hot air engine and hydraulic fluid in a hydraulic motor or hydraulic cylinder. More generally, in a thermodynamic system, the working fluid is a liquid or gas that absorbs or transmits energy.


PROFIBUS (Process Field Bus) is a standard for fieldbus communication in automation technology and was first promoted in 1989 by BMBF (German department of education and research) and then used by Siemens. It should not be confused with the PROFINET standard for Industrial Ethernet.

Proof Pressure

Proof pressure (normally 1.5 times system pressure) is the maximum pressure which may be applied to any pressure sensor without causing permanent damage.

Proof Temperature

The maximum temperature of the media which the sensing portion of the switch can be subjected to without causing permanent damage.

Proportional Band

The PID parameter which determines the area in which the proportional control algorithm is operative.

Proportional Control

(1) Current or Voltage: Control algorithm which determines a continuous linear relationship between the input and the output.

(2) Time proportioning: Control algorithm that determines the time that a control output remains in the "ON" condition in a finite cycle. In this case, when the output is "ON", it is fully on.

Propylene Glycol

An organic compound, it is a viscous, colourless liquid which is nearly odourless.

Chemically it is miscible with a broad range of solvents, including water, acetone, and chloroform.

It is used in the production of unsaturated polyester resins and thermoset plastics.


A set of rules used in generating or receiving a message to insure reliable digital or other communications. It may involve transaction rules, message structure, coding, and physical signal characteristics.

Proximity Sensor

A sensor able to detect the presence of nearby objects without any physical contact.

A proximity sensor often emits an electromagnetic field or a beam of electromagnetic radiation and looks for changes in the field or return signal. The object being sensed is often referred to as the proximity sensor's target. Different proximity sensor targets demand different sensors. For example, a capacitive or photoelectric sensor might be suitable for a plastic target; an inductive proximity sensor always requires a metal target. Proximity sensors can have a high reliability and long functional life because of the absence of mechanical parts and lack of physical contact between sensor and the sensed object.

Proximity sensors are commonly used in machine vibration monitoring to measure the variation in distance between a shaft and its support bearing. This is common in large steam turbines, compressors, and motors that use sleeve-type bearings. International Electrotechnical Commission (IEC) 60947-5-2 defines the technical details of proximity sensors.


The pressure resulting from a force of one pound-force applied to an area of one square inch.


Pounds per square inch absolute.

Pressure referenced to a vacuum.


Pounds per square inch gauge.

Pressure referenced to ambient air pressure.


PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible.

PVC is commonly used as the insulation on electrical cables; PVC used for this purpose needs to be plasticized. In a fire, PVC-coated wires can form hydrogen chloride fumes; the chlorine serves to scavenge free radicals and is the source of the material's fire retardance. Frequently in applications where smoke is a major hazard (notably in tunnels and communal areas) PVC-free cable insulation is preferred, such as low smoke zero halogen (LSZH) insulation.

The rigid form of PVC is used in construction for pipe and in profile applications such as doors and windows. It can be made softer and more flexible by the addition of plasticizers. In this form, it is also used in plumbing, electrical cable insulation and many applications where it replaces rubber.


A highly non-reactive and pure thermoplastic fluoropolymer.

PVDF is commonly used as insulation on electrical wires, because of its combination of flexibility, low weight, low thermal conductivity, high chemical corrosion resistance, and heat resistance. The piezoelectric properties of PVDF are used to manufacture tactile sensor arrays, inexpensive strain gauges and lightweight audio transducers. PVDF transducers have the advantage of being dynamically more suitable for modal testing applications than semi-conductor piezoresistive transducers, and more compliant for structural integration than piezoceramic transducers.

Ramp Rate

The number of degrees (Fahrenheit or Celsius) that the media will increase in a unit of time (minute or second).


The upper and lower pressure limits that a transducer is required to measure.

Rate Time

The time interval over which the system variable is sampled for the derivative function.


The relation between two similar magnitudes in respect to the number of times the first contains the second.

Ratiometric Measurement

A resistance measurement technique where the unknown resistance is placed in series with a known resistance. The voltage across each is measured to determine the unknown resistance.


The opposition presented by capacitance and/or inductance to the passage of alternating current of a given frequency.

Rectifier-Type Meter

A DC meter equipped with a solid-state rectifier at its input to convert AC energy to DC energy. The instrument provides measurements of the average value of an AC voltage or current, and its scale is usually calibrated in terms of the RMS equivalent. Such calibration is accurate for pure sine-wave signals, but the accuracy decreases for distorted signals.


The quality possessed by carbon steel that suffers from having too much sulfur as an impurity.

Reference Junction

The cold junction in a thermocouple circuit, which is held at a stable known temperature.

The standard reference temperature is 0°C (32°F); however, other temperatures can be used.

Reference RTD

The Reference RTD detects and outputs a signal to the Electronics Module which is proportionate to the process media temperature.


Waste material that has been reclaimed by shredding or granulating.

Regulated Vacuums

Control of pressure in a vessel at pressures less than atmospheric.


A device which has the function of maintaining a designated characteristic. It performs the activity of managing or maintaining a range of values in a machine. The measurable property of a device is managed closely by specified conditions or an advance set value; or it can be a variable according to a predetermined arrangement scheme. It can be used generally to connote any set of various controls or devices for regulating or controlling items or objects.

Examples are a voltage regulator, a pressure regulator, such as a diving regulator, which maintains its output at a fixed pressure lower than its input, and a fuel regulator, which controls the supply of fuel. Regulators can be designed to control anything from gases or fluids, to light or electricity.


Mechanical: An electromagnetic device that completes or interrupts a circuit by physically moving electrical contacts into contact with each other.

Mercury Displacement: A power switching device in which mercury, displaced by a plunger, completes the electric circuit across contacts.

Solid state: A solid-state switching device which completes or interrupts a circuit electrically with no moving parts.

Relief Diaphragm

A diaphragm assembly feature that allows exhausting to the atmosphere when regulated output pressure exceeds a set pressure point.

Remote Setpoint

An analog input to a controller which allows the setpoint to be changed by a remote device. This can be another instrument (cascading), a PLC, or computer or it can be done manually.


Repeatability is the maximum operational set point deviation of a single sensor (a pressure, temperature, or flow switch) under one given set of environmental and operational conditions.


A procedure allowing the modifications of configuration values and parameters that change the transmitter 4-20 mA output settings in response to input pressure readings.


An intrinsic property that quantifies how strongly a given material opposes the flow of electric current. A low resistivity indicates a material that readily allows the movement of electric charge.

Resistivity is commonly represented by the Greek letter ρ (rho).


The degree to which nearly equal values of a quantity can be discriminated.

In digital meters, the value represented by a one-digit change in the least-significant digit.

Response Time

The amount of time (in seconds) in which the sensor operates after being subjected to a step temperature increase where the difference between the initial soak temperature and actuation temperature equals 63% of the step temperature.

The response time is expressed for a designated flow (feet per second), media and system pressure (PSIG).

Reverse Acting

Control output that decreases as the process variable increases. In the case of an alarm, the reverse acting alarm has its relay activated in the non-alarm state.

This is also called fail-safe alarm.


A disturbance that affects an electrical circuit due to either electromagnetic induction or electromagnetic radiation emitted from an external source. Closely related to EMI, RFI refers specifically to Radio Frequency Interference.

Rise Rate

The number of degrees (Fahrenheit or Celsius) that the media will increase in a unit of time (minute or second). See Also: Ramp Rate


European Union directive aimed at restricting the use of certain hazardous substances commonly found in electrical and electronic equipment. A product that is RoHS compliant has none (or very little) of these hazardous substances.

Room Condition

Ambient conditions used for test purposes.

Root Mean Square

The square root of the mean of the square of the signal over one full cycle.

Effective heating value.


This is estimated uncertainty of the measurement. In RSS analysis, each of the errors is squared, Then, they are added together and the square root is taken. RSS analysis is appropriate when: there are several sources of uncertainty or no one source dominates or the uncertainties are not correlated.


Resistance Temperature Detector. A metallic sensor where resistance increases in a predictable manner with increasing temperature.


RTFE (reinforced Teflon®) is mixed with a percentage of glass filler material to provide additional strength, stability, resistance to abrasive wear, and less permeation.


Rostechnadzor Permit for especially dangerous industrial objects. The EIOs (Especially dangerous Industrial Objects) that are subject to registration include toxic, flammable, explosive, combustible, highly toxic and oxidizing materials, and any other materials that may be harmful to the environment.

SAE International

Initially established as the Society of Automotive Engineers, SAE is a U.S.-based, globally active professional association and standards organization for engineering professionals in various industries. Principal emphasis is placed on transport industries such as automotive, aerospace, and commercial vehicles. SAE International coordinates the development of technical standards based on best practices identified and described by SAE committees and task forces. Task forces are composed of engineering professionals from relevant fields. Aside from its standardization efforts, SAE International also devotes resources to projects and programs in STEM education, professional certification, and collegiate design competitions.

SAE Thread

A standard for inch based threaded fasteners and washers. Together with the USS Standard Thread, it was incorporated into the Unified Thread Standard.

However, the term continues to be used occasionally today to describe inch based threaded fasteners with a coarse thread pitch. The Unified Thread Standard uses the term UNC (Unified National Coarse) to describe a fastener that previously would have been designated USS and the Unified Thread Standard uses the term UNF (Unified National Fine) to describe a fastener that would have previously been designated SAE.

SAF 2507

A Sandvik-owned trademark for a 25Cr duplex (ferritic-austenitic) stainless steel. Typical properties of SAF 2507 duplex stainless steel are:

High resistance to corrosion

High mechanical strength

High resistance to erosion corrosion and corrosion fatigue

Good weldability

Safe Overexposure

The maximum pressure that can be applied to a transducer without changing its performance beyond specified tolerances.


The sapphire is one of the three gem-varieties of corundum.

Because of the remarkable hardness of sapphires –the third hardest mineral– and of aluminium oxide in general, sapphires are used in some non-ornamental applications, including infrared optical components, such as in scientific instruments; high-durability windows; wristwatch crystals and movement bearings; and very thin electronic wafers, which are used as the insulating substrates of very special-purpose solid-state electronics.

Secondary Junction

An unwanted connection between a pair of thermocouple wires tending to produce a signal representative of the secondary junction temperature rather than the measuring junction temperature.

Seismic Shock and Vibration

Low frequency, high amplitude waves produced as a result of earth movement.

CCS pressure sensors are generally unaffected by seismic shock and vibration.

Self Heating

Internal heating of a transducer as a result of power dissipation.

Self Regulation

The property of a process or machine which permits attainment of equilibrium, after a disturbance, without the intervention of a controller.


The minimum change in input to which a device can respond.

Sensitivity Shift

A change in the calibration slope.


A sensing element. The basic element that usually changes some physical parameter to an electrical signal.

Set Point

An input variable which sets the desired value of a controlled variable.

Settling Time

The time required for the output to settle within a specified band of the final value when a step input change is applied.

Shear Stress

A tangential force divided by the area (FORCE/AREA) on which it is applied.

The shear stress is equal to the viscosity multiplied by the shear rate (measured in units of pressure, i.e., MPa or psi).

At the die lips under usual production conditions, the shear stress may reach values of 0.2 MPa (29.0 psi) or more. The usually accepted value for the onset of sharkskin in capillaries is 0.14 MPa (20.3 psi), although higher values are reported in industrial production. With additives the critical shear stress value might be pushed up to 0.5 MPa (72.5 psi).

Shear Viscosity

The ordinary viscosity that is the ratio of shear stress to the shear rate.


A protective enclosure surrounding a circuit or cable which is to protect it from an electrical disturbance such as noise.


A calibrated low resistance connected in parallel with the input terminals of an ammeter in order to enable measurement of higher currents. It can be internal or external. Typical external shunts are either 50mV or 100mV full scale.

Shunt Calibration/Rcal

A method of generating an electrical output to match the electrical output that would be given in response to an applied pressure.

This is accomplished using a resistor to unbalance the bridge electrically rather than with strain introduced by applied pressure. With standardized shunt or Rcal, the same point (generally 80%) is chosen on the calibration curve so that all similar transducers calibrate at the same point to facilitate interchangeability.

Signal Conditioner

An electronic network that permits adjustments to match a particular transducer to a readout device.

Generally included are provisions for adjusting for zero balance and span or sensitivity.

Signal Conditioning

To process the form or mode of a signal so as to make it intelligible to, or compatible with, a given device, including such manipulation as pulse shaping, pulse clipping, digitizing, and linearizing.


Safety integrity level (SIL) is defined as a relative level of risk-reduction provided by a safety function, or to specify a target level of risk reduction. In simple terms, SIL is a measurement of performance required for a safety instrumented function (SIF).

The requirements for a given SIL are not consistent among all of the functional safety standards. In the European functional safety standards based on the IEC 61508 standard four SILs are defined, with SIL 4 the most dependable and SIL 1 the least. A SIL is determined based on a number of quantitative factors in combination with qualitative factors such as development process and safety life cycle management.

Assignment of SIL is an exercise in risk analysis where the risk associated with a specific hazard, that is intended to be protected against by a SIF, is calculated without the beneficial risk reduction effect of the SIF. That "unmitigated" risk is then compared against a tolerable risk target. The difference between the "unmitigated" risk and the tolerable risk, if the "unmitigated" risk is higher than tolerable, must be addressed through risk reduction of the SIF. This amount of required risk reduction is correlated with the SIL target. In essence, each order of magnitude of risk reduction that is required correlates with an increase in one of the required SIL numbers.


Any inert, synthetic compound made up of repeating units of siloxane.

They are typically heat-resistant and rubber-like, and are used in sealants, adhesives, lubricants, and thermal and electrical insulation. Electronic components are sometimes encased in silicone to increase stability against mechanical and electrical shock, radiation and vibration, also known as "potting". Silicones are used where durability and high performance are demanded of components under hard conditions, such as in space (satellite technology). They are selected over polyurethane or epoxy encapsulation when a wide operating temperature range is required (−65 to 315 °C). Silicones also have the advantage of little exothermic heat rise during cure, low toxicity, good electrical properties and high purity.

The use of silicones in electronics is not without problems, however. Silicones are relatively expensive and can be attacked by solvents. Silicone easily migrates as either a liquid or vapor onto other components. Silicone contamination of electrical switch contacts can lead to failures by causing an increase in contact resistance, often late in the life of the contact, well after any testing is completed. Use of silicone-based spray products in electronic devices during maintenance or repairs can cause later failures.

Silicone Oil

Silicone oils are primarily used as lubricants, thermic fluid oils or hydraulic fluids. They are excellent electrical insulators and, unlike their carbon analogues, are non-flammable.

Silicone oil is also commonly used as the working fluid in dashpots, wet type transformers, diffusion pumps and in oil-filled heaters.

Silicone Rubber

An elastomer composed of silicone polymer. Silicone rubbers are widely used in industry in various formulations.

Silicone rubber is generally non-reactive, stable, and resistant to extreme environments and temperatures from -55 °C to +300 °C while still maintaining its useful properties. Some properties such as elongation, creep, cyclic flexing, tear strength, compression set, dielectric strength (at high voltage), thermal conductivity, fire resistance and in some cases tensile strength can be far superior to organic rubbers in general. Silicone rubber is a material of choice in industry when retention of initial shape and mechanical strength are desired under heavy thermal stress or sub-zero temperatures. Silicone Rubber Cord can be joined to make O-rings and extruded profiles can be joined to make seals. Silicone rubber tape with an iron-oxide additive is used extensively in aviation and aerospace wiring applications as a splice or wrapping tape due to its non-flammable nature. The iron-oxide additive adds high thermal conductivity but does not change the high electrical insulation property of the silicone rubber. This type of self-amalgamating tape fuses to itself, so that when stretched and wrapped around cables, electrical joints, hoses and pipes it bonds into a strong seamless rubbery electrically insulating and waterproof layer, although not adhesive. With the addition of carbon or another conductive substance as a powdered filler, silicone rubber can be made electrically conductive while retaining most of its other mechanical properties.


The name that is used in some countries for alloys based on the Al–Si system. Silumin is a series of lightweight, high-strength aluminium alloys with silicon content within range of 3–50%.

Among the advantages of silumin is its high resistance to corrosion, making it useful in humid environments. The addition of silicon to aluminium also makes it less viscous when liquid, which together with its low cost (both component elements are relatively cheap to extract), makes it a very good casting alloy. The benefits of Silumin include its high castability and machinability, high fluidity and high corrosion resistance. It is ductile with a low specific gravity and good ability to operate under heavy load conditions.


A soft, lustrous transition metal, it possesses the highest electrical conductivity, thermal conductivity and reflectivity of any metal.

Silver is used industrially in electrical contacts and conductors, in specialized mirrors and in catalysis of chemical reactions. Some electrical and electronic products use silver for its superior conductivity, even when tarnished. The primary example of this is in high quality RF connectors. Silver cadmium oxide is used in high-voltage contacts because it can withstand arcing.


Duplex communications refer to communications in one direction only.

Single Ended Input

Amplifier with one input referenced to circuit common or ground.

Single Stage Regulator

A pressure reducing regulator which reduces supply (inlet) pressure to output (controlled) pressure with a single pressure sensing element and control valve. Single stage regulators are typically used when supply pressure is constant (such as a pipeline regulator), or where frequent adjustment is not a problem.


A world leader in the conformity assessment solutions field, specializing in explosion safety of equipment used in potentially explosive atmospheres (ATEX & IECEx). As a leading Notified Body for Ex Product Certification (ATEX & IECEx), Sira sets the standard with a range of ATEX 137 & DSEAR, ATEX Quality Assurance, IEC 61508 Functional Safety, Training and Personnel Competence Certification services. In 2009, Sira became a CSA International company and provides certification to North American requirements.


The communication device which is controlled by a Master device in a communications environment. In a Master-Salve operation, the Slave device can only respond when requested by the Master device.


A resistance/capacitor or diode/resistor network used to dissipate switching transients. Often used across high current relay contacts.


A solenoid is a type of electromagnet when the purpose is to generate a controlled magnetic field. If the purpose of the solenoid is instead to impede changes in the electric current, a solenoid can be more specifically classified as an inductor rather than an electromagnet.


The algebraic difference between the upper and lower range values.

Span Adjustment

The ability to adjust the gain of a process or meter so the display span corresponds to a specified signal span.

Span Error

The value of the error produced when an instrument amplifies the measured quantity in some manner so as the signal gets larger or smaller than its perceived value.

Span Turndown

The ability to re-range a transmitter to lower ranges. The re-ranging allows the 20 mA signal to be adjusted to the lower range which provides improved resolution.

SPDT (Single Pole Double Throw)

A SPDT switching element has one normally open, one normally closed and one common terminal. Three terminals mean that the switch can be wired with the circuit either normally open (N/O) or normally closed (N/C).


The ability of a transducer to retain its performance characteristics for a period of time and under a variety of conditions.

Stainless Steel

Stainless steel does not readily corrode, rust or stain with water as ordinary steel does. However, it is not fully stain-proof in low-oxygen, high-salinity, or poor air-circulation environments. There are different grades and surface finishes of stainless steel to suit the environment the alloy must endure. Stainless steel is used where both the properties of steel and corrosion resistance are required.

Standard Cubic Feet per Hour

Standard cubic feet per hour (SCFH) is the volumetric flow rate of a gas corrected to "standardized" conditions of temperature and pressure. It is related to the mass flow rate of the gas by a multiplicative constant which depends only on the molecular weight of the gas.

There are different standard conditions for temperature and pressure, so care is taken when choosing a particular standard value. Worldwide, the "standard" condition for pressure is variously defined as an absolute pressure of 101,325 pascals, 1.0 bar (i.e., 100,000 pascals), 14.73 psia, or 14.696 psia and the "standard" temperature is variously defined as 68 °F, 60 °F, 0 °C, 15 °C, 20 °C, or 25 °C. The relative humidity (e.g., 36% or 0%) is also included in some definitions of standard conditions.

Standard Cubic Feet per Minute

Standard cubic feet per minute (SCFM) is the volumetric flow rate of a gas corrected to "standardized" conditions of temperature and pressure. It is related to the mass flow rate of the gas by a multiplicative constant which depends only on the molecular weight of the gas.

There are different standard conditions for temperature and pressure, so care is taken when choosing a particular standard value. Worldwide, the "standard" condition for pressure is variously defined as an absolute pressure of 101,325 pascals, 1.0 bar (i.e., 100,000 pascals), 14.73 psia, or 14.696 psia and the "standard" temperature is variously defined as 68 °F, 60 °F, 0 °C, 15 °C, 20 °C, or 25 °C. The relative humidity (e.g., 36% or 0%) is also included in some definitions of standard conditions.


A characteristic of a condition, such as value, rate, periodicity or amplitude, exhibiting only negligible change over an arbitrary long period.

Static Calibration

A calibration recording pressure versus output at room temperature.

Static Error Band

The error band applicable at room temperature.

Static Pressure

The pressure of a fluid or gas at rest.


A measure of deformation representing the displacement between particles in the body relative to a reference length.

Strain Gauge

A measuring element for converting force, pressure, tension, etc., into an electrical signal.

Supply Current

The amount of current necessary to maintain operation of a photoelectric control, proximity sensor or control base.

Expressed in amps or milliamps.

Sometimes referred to as Current Consumption.

Supply Pressure Effect

The effect of supply pressure variations relative to output pressure at a constant set point.

Supply Voltage

The range of power required to maintain proper operation of a photoelectric control, proximity sensor or control base. The difference in potential (or range of difference in potential) necessary to operate the unit.

Expressed in volts.


An instability of melt pressure and flow rate in an extruder, which can be detected by a pressure gage at the tip of the screw (or at the die adapter), or by dimensional product variations.


A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. The mechanism of a switch may be operated directly by a human operator to control a circuit (for example, a light switch or a keyboard button), may be operated by a moving object such as a door-operated switch, or may be operated by some sensing element for pressure, temperature or flow. Switches are made to handle a wide range of voltages and currents; very large switches may be used to isolate high-voltage circuits in electrical substations.


Syltherm XLT and Syltherm 800 are highly stable, long lasting silicone based heat transfer fluids specially formulated for use in low, medium and high temperature systems.

Syltherm XLT heat transfer fluid has a recommended use range from -150°F (-101°C) to 500°F (260°C). Syltherm 800 heat transfer fluid is also a highly stable, long lasting silicone based product designed for high temperature liquid-phase operation. It has a recommended operating temperature range of -40°F (-40°C) to 750°F (400°C). Operating continuously at the upper end of this range, Syltherm 800 fluid exhibits low potential for fouling and can often remain in service for 10 years or more. Slytherm's advantages include a low freezing point, high temperature stability and great longevity. It is non-corrosive with low odor and a low acute oral toxicity.

Synchronous Motor

An AC motor whose speed is exactly proportional to the frequency of the applied alternating voltage.

Synthetic Rubber

Any type of artificial elastomer mainly synthesised from petroleum byproducts. Synthetic rubber, like natural rubber, has uses in hoses, belts, matting, O rings, gaskets, oil seals, V belts and as cable jacketing.

System Pressure

The nominal pressure level that a system will operate at including work load.


A German air pollution control regulation.

Among other things, it regulates emission limits for hazardous, toxic, carcinogenic or mutagenic substances and air pollutant emissions.


A rare, hard transition metal that is highly corrosion-resistant.

The chemical inertness of tantalum makes it a substitute for platinum. Its main use is in tantalum capacitors in electronic equipment. The major use for tantalum powder is in the production of electronic components such as capacitors and high-power resistors. Tantalum is also used to produce a variety of alloys that have high melting points and strength.

Because of its high ductility, tantalum can be drawn into fine wires or filaments, which are used for evaporating metals such as aluminum. Tantalum is inert against most acids. Tantalum was extensively used in the production of ultra high frequency electron tubes for radio transmitters.

Tapped Exhaust Connection

Tapped exhaust simply means the exhaust port is tapped so you can plumb off the exhaust through an attached piece of piping.

This may be desirable if the media is natural gas, for example, or if you would like to have the exhaust vented away from the immediate relay location. This does not affect the operation of the relay.

Taut Band

Method of suspending moving coil or moving iron vane in magnetic field. Eliminates pivot and jewel friction problems.


Any plastic material used to fabricate something usually made of metal.


A synthetic fluoropolymer of tetrafluoroethylene that has numerous applications.

Teflon is hydrophobic: neither water nor water-containing substances wet Teflon. Teflon has one of the lowest coefficients of friction against any solid. It is very non-reactive, partly because of the strength of carbon–fluorine bonds so it is often used in containers and pipework for reactive and corrosive chemicals.

Where used as a lubricant, teflon reduces friction, wear and energy consumption of machinery. The major application of Teflon is for wiring in aerospace and computer applications (e.g. hookup wire, coaxial cables). This application exploits the fact that Teflon has excellent dielectric properties. This is especially true at high radio frequencies, making it suitable for use as an insulator in cables and connector assemblies and as a material for printed circuit boards used at microwave frequencies. Combined with its high melting temperature, this makes it the material of choice as a high-performance substitute for the weaker and lower-melting-point polyethylene commonly used in low-cost applications.

Temperature Compensation

The utilization of supplementary devices, materials or components within the bridge to minimize sources of error caused by changing temperature.

Temperature Compensation Range

This is the range of temperature within which the transducer output is electronically corrected for errors induced by changes to materials or bridge resistance due to temperature. This is also the range of temperature within which all tolerances specified for Thermal Zero Shift and Thermal Sensitivity Shift are applicable (temperature error).

Temperature Effect on Span

The percentage change in rated output per degree change in ambient temperature.

Temperature Effect on Zero

The percentage change in zero balance due to a change in ambient temperature.

Temperature Lag

The number of degrees above the actuation point that the media will be when the sensor operates.

The lag is expressed for a designated rise rate (degrees per second), flow (feet per second), and system pressure (PSIG). The lag is determined by multiplying the rise rate by the response time. Example: If a system with a constant flow, pressure, and rise rate of 10 °F per second incorporated a sensor with a response time of 3 seconds, the lag would be 30 degrees.

Temperature Range, Compensated

The range of ambient temperature for which Thermal Zero Shift is applicable (temperature error). Operation outside this range may require re-calibration.

Temperature Range, Operable

The range of ambient temperature, given by their extremes, within which the transducer is intended to operate.

Temperature Range, Storage

The range of ambient temperatures, given by their extremes, at which a transducer may be stored or transported.

Temperature Switch

A temperature switch is a sensor that upon the increase or decrease of a temperature, opens or closes one or more electrical switching elements at a predetermined set point.

Tempered Glass

A type of safety glass processed by thermal or chemical treatments to increase its strength compared with normal glass.

Tempering puts the outer surfaces into compression and the inner surfaces into tension. Such stresses cause the glass, when broken, to crumble into small granular chunks instead of splintering into jagged shards as plate glass creates. The granular chunks are less likely to cause injury. The water rapidly cools the molten glass on the outside, while the inner portion of the glass remains significantly hotter. When the glass on the inside eventually cools, it contracts inside the already-solid outer part. This contraction sets up very large compressive stresses on the surface, while the core of the drop is in a state of tensile stress. As a result of its safety and strength, toughened glass is used in a variety of demanding applications.

Terminal Block

Terminal blocks (also called terminal boards or strips) provide a convenient means of connecting individual electrical wires without a splice or physically joining the ends. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items. Since terminal blocks are readily available for a wide range of wire sizes and terminal quantity, they are one of the most flexible types of electrical connector available. Some disadvantages are that connecting wires is more difficult than simply plugging in a cable and the terminals are generally not very well protected from contact with persons or foreign conducting materials.

Thermal Conductivity

The ability of a substance to transmit heat by conduction.

Thermal Gradient

A continuously changing temperature as a function of distance.

Thermal Mechanical

Analysis In this technique, a sample is deformed under a static load as its temperature is being changed.

Glass transition and softening points can be measured. The amount of orientation can also be measured by TMA.

Thermal Sensitivity Shift

The sensitivity shift due to changes of the ambient temperature from room temperature to the specified limits of the compensated temperature range.

Thermal Zero Shift

An error due to changes in ambient temperature in which the zero pressure output shifts. Thus, the entire calibration curve moves in parallel displacement.


A semiconductor material which exhibits a known electrical resistance vs. temperature.


The junction of two dissimilar metals which has a voltage output proportional to the difference in temperature between the hot junction and the lead wires connected to the sensing device (cold junction).

Thermocouple Break Protection

A means to indicate when thermocouple has failed in an open circuit condition.

Thermocouple Connector

A special polarized disconnect device whose current-carrying parts are of thermocouple alloy material.

Thermocouple Loop Resistance

The total resistance of the thermocouple and its extension wire.


A device that measures temperature or a temperature gradient.

A thermometer has two important elements: (1) a temperature sensor (e.g. the bulb on a mercury-in-glass thermometer) in which some physical change occurs with temperature, and (2) some means of converting this physical change into a numerical value (e.g. the visible scale that is marked on a mercury-in-glass thermometer). There are various principles by which different thermometers operate. They include the thermal expansion of solids or liquids with temperature, or the change in pressure of a gas on heating or cooling. Radiation-type thermometers measure the infrared energy emitted by an object, allowing measurement of temperature without contact.

Thermometers are widely used in industry to control and regulate processes, in the study of weather, in medicine, and scientific research.


A number of thermocouples connected in series, arranged so that alternate junctions are the referenced temperature and at the measured temperature to increase the output for a give temperature difference between the measuring and reference junctions.


A plastic material, polymer, that becomes pliable or moldable above a specific temperature and solidifies upon cooling. They should be differentiated from thermoset materials which cure, or become set, when they are heated. Thermoplastic materials are melt processable, that is they are formed when they are in a melted or viscous phase. This generally means they are heated, formed, then cooled in their final shape.


Materials that undergo chemical reaction and can be hardened by application of heat and pressure. They cannot be softened again to make them flowable. Typical plastics in this family are melamine, urea, epoxies and phenolics.


A housing that can be provided with temperature switches to isolate the temperature probe from the media.

Time Constant

The amount of time (in seconds) in which the sensor operates after being subjected to a step temperature increase where the difference between the initial soak temperature and actuation temperature equals 63% of the step temperature.

The response time is expressed for a designated flow (feet per second), media and system pressure (PSIG).


A lustrous transition metal with low density and high strength. It is highly resistant to corrosion in sea water, aqua regia and chlorine. Welded titanium pipe and process equipment (heat exchangers, tanks, process vessels, valves) are used in the chemical and petrochemical industries primarily for corrosion resistance.

Specific alloys are used in downhole and nickel hydrometallurgy applications due to their high strength (e. g.: titanium Beta C alloy), corrosion resistance, or combination of both. The pulp and paper industry uses titanium in process equipment exposed to corrosive media such as sodium hypochlorite or wet chlorine gas (in the bleachery). Other applications include: ultrasonic welding, wave soldering, and sputtering targets. Due to its high corrosion resistance to sea water, titanium is used to make propeller shafts and rigging and in the heat exchangers of desalination plants.


In the broadest sense it is a device (or medium) that converts one energy form to another. Therefore, items such as a windmill, electric light, or an automobile engine could be called a "transducer" - but, in common practice, the term is generally applied to devices that take a physical phenomenon (pressure, temperature, humidity, flow, etc.) and converts it to an electrical output.


A transistor is a semiconductor device used to amplify or switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current through another pair of terminals. Because the controlled (output) power can be higher than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits. The transistor is the fundamental building block of modern electronic devices, and is ubiquitous in modern electronic systems.


A device which translates the low-level output of a sensor or transducer to a higher level signal which is suitable for transmission to a site where it can be processed further.


A process in which materials contact one another, rub, and then separate, each with a resulting charge distribution. This process is familiar and applied extensively in processes such as electrophotography and energy harvesting, but it is not completely understood.

Tungsten Carbide

A carbide containing equal parts of tungsten and carbon atoms. In its most basic form, tungsten carbide is a fine gray powder, but it can be pressed and formed into shapes for use in industrial machinery, cutting tools, abrasives, armor-piercing rounds and other tools and instruments.

Tungsten carbide is approximately two times stiffer than steel, and is much denser than steel or titanium. It is comparable with corundum in hardness and can only be polished and finished with abrasives of superior hardness such as cubic boron nitride and diamond powder, wheels, and compounds.

Turndown Ratio

The width of the operational range of a device.

Defined as the ratio of the maximum capacity to minimum capacity. For example, a device with a maximum output of 10 units and a minimum output of 2 units has a turndown ratio of 5.

The term is commonly used with measurement devices and combustion plant like boilers and gasifiers.


A subset of the thermoplastic polyethylene.

It is a very tough material, with the highest impact strength of any thermoplastic presently made. UHMWPE is odorless, tasteless, and nontoxic. It is highly resistant to corrosive chemicals except oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating; and is highly resistant to abrasion, in some forms being 15 times more resistant to abrasion than carbon steel. Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to that of polytetrafluoroethylene (PTFE, Teflon), but UHMWPE has better abrasion resistance than PTFE.

UL (Underwriters Laboratories)

A nonprofit corporation engaged in developing standards and testing for safety. Products bearing UL labels have been tested for conformity to UL standards. UL maintains a product surveillance program to ensure continuing conformity to UL standards.

UL Listed Product

A product that has been tested and complies to UL requirements for reasonably foreseeable hazards associated with the product and is subject to continuing UL product surveillance. UL authorizes the manufacturer to use the UL Listing mark.

UL Recognized Component

A part or subassembly that has been tested and complies to UL requirements for components used in an end product which complies with UL requirements. The component is subject to continuing UL surveillance. UL authorizes the manufacturer to use the UL Recognized mark.


Underwriters Laboratories of Canada (ULC) is an independent product safety testing, certification and inspection organization accredited by the Standards Council of Canada under the National Standards System. ULC Standards is an independent, not-for-profit standards development organization. These standards play an important part in improving public safety. ULC Standards employs a consensus-based process of developing effective product safety standards, using input from consumers, manufacturers, government agencies, users, regulatory authorities and other interested parties. ULC evaluates a broad range of products, components, materials and systems for compliance to specific requirements. Today, ULC helps companies bring safer products to Canadian and global marketplaces. ULC’s safety certification services include testing, evaluation and factory surveillance of products to Canadian and international standards for safety. These certifications enhance the safety of products as well as the public’s confidence in their compliance. Consumers, retailers, insurers, distributors and regulators recognize our familiar Marks as trusted symbols of safety.

UNF Connections

A standard thread form and series—along with allowances, tolerances, and designations—for screw threads commonly used in the United States and Canada. It is the main standard for bolts, nuts, and a wide variety of other threaded fasteners used in these countries. It has the same 60° profile as the ISO metric screw thread, but the characteristic dimensions of each UTS thread (outer diameter and pitch) were chosen as an inch fraction rather than a millimeter value. The UTS is currently controlled by ASME/ANSI in the United States.


In electronic meters, a capability for measuring voltage or current of only one polarity, [i.e., the (+) or (-)].

Upper Range Limit

The highest value of the measured variable that the analog output of the transmitter is capable of measuring. Upper Range Limit, URL, is factory set and not modifiable by the user.

Upper Range Value

The highest value of the measurand that the analog output of the transmitter is currently configured to measure. Upper Range Value, URV, is a user settable entity.


A device that regulates, directs or controls the flow of a fluid by opening, closing, or partially obstructing various passageways. In an open valve, fluid flows in a direction from higher pressure to lower pressure.

Valves are found in virtually every industrial process, including water & sewage processing, mining, power generation, processing of oil, gas & petroleum, food manufacturing, chemical & plastic manufacturing and many other fields. Valves may be operated manually, either by a handle, lever, pedal or wheel. Valves may also be automatic, driven by changes in pressure, temperature, or flow. These changes may act upon a diaphragm or a piston which in turn activates the valve. More complex control systems using valves requiring automatic control based on an external input (i.e., regulating flow through a pipe to a changing set point) require an actuator. An actuator will stroke the valve depending on its input and set-up, allowing the valve to be positioned accurately, and allowing control over a variety of requirements.

Vent Port

A feature of some regulators which permits the user to install a fluid connector into a regulator bonnet (control spring chamber) and pipe away any fluid which enters the bonnet. Capture ports are used when the user needs to contain the regulated media in case of catastrophic failure of the pressure sensing element, or when self-relieving is required. Capture ports may be user-positionable or fixed depending on the model.


A mechanical phenomenon whereby oscillations occur about an equilibrium point. The oscillations may be periodic such as the motion of a pendulum or random such as the movement of a tire on a gravel road. Generally, vibration is undesirable, wasting energy and creating unwanted noise. For example, the vibrational motions of engines, electric motors, or any mechanical device in operation are typically unwanted. Such vibrations can be caused by imbalances in the rotating parts, uneven friction, the meshing of gear teeth, etc. Careful designs usually minimize unwanted vibrations. The study of sound and vibration are closely related. Hence, when trying to reduce noise it is often a problem in trying to reduce vibration.


A measure of its resistance to gradual deformation by shear stress or tensile stress. For liquids, it corresponds to the informal concept of "thickness". For example, honey has a much higher viscosity than water. Viscosity is a property arising from collisions between neighboring particles in a fluid that are moving at different velocities. A liquid is said to be viscous if its viscosity is substantially greater than that of water; and may be described as mobile if the viscosity is noticeably less than water. A fluid with a relatively high viscosity, for example, pitch, may appear to be a solid.


Viton® is a brand of synthetic rubber and fluoropolymer elastomer commonly used in O-rings, chemical-resistant gloves, and other molded or extruded goods. The name is a registered trademark of DuPont Performance Elastomers L.L.C..

Viton fluoroelastomers are categorized under the ASTM D1418 and ISO 1629 designation of FKM. This class of elastomers is a family comprising copolymers of hexafluoropropylene (HFP) and vinylidene fluoride (VDF or VF2), terpolymers of tetrafluoroethylene (TFE), vinylidene fluoride (VDF) and hexafluoropropylene (HFP) as well as perfluoromethylvinylether (PMVE) containing specialties. The fluorine content of the most common Viton grades varies between 66 and 70%.

Voltage Drop

The amount of voltage loss that occurs through all or part of a circuit due to impedance. A common analogy used to explain voltage, current and voltage drop is a garden hose: voltage is analogous to the water pressure supplied to the hose and the inherent resistance of the hose is determined by the type and size of the hose - just like the type and size of an electrical wire determines its resistance.


Wavelength is the distance between two identical adjacent points in a wave. It is typically measured between two easily identifiable points, such as two adjacent crests or troughs in a waveform. While wavelengths can be calculated for many types of waves, they are most accurately measured in sinusoidal waves, which have a smooth and repetitive oscillation.

Weep Hole

A small opening that allows fluid to drain from within an assembly. Weeps are located at the bottom of the object to allow for drainage; the weep hole must be sized adequately to overcome surface tension.

Wetted Parts

Materials in a sensor that are directly exposed to the media.

Wheatstone Bridge

An electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a wheatstone bridge is its ability to provide extremely accurate measurements (in contrast with something like a simple voltage divider). The Wheatstone bridge illustrates the concept of a difference measurement, which can be extremely accurate. Variations on the Wheatstone bridge can be used to measure capacitance, inductance, impedance and other quantities, such as the amount of combustible gases in a sample, with an explosimeter.

Zero Adjustment

Means of adjusting the zero pressure output of an amplified transducer.

Zero Balance

The measured transducer output under room conditions with no pressure applied to the pressure port. For absolute pressure transducers, this value is measured at 0 psia. Gage and sealed pressure transducers have this value measured at atmospheric pressure.

Zero Error

Any indication that a measuring system gives a false reading when the true value of a measured quantity is zero, e.g. the needle on an ammeter failing to return to zero when no current flows. A zero error may result in a systematic uncertainty.

Zero Shift

Any parallel shift of the input/output curve.

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