Common Process Control Terminology

Scroll down or click on the category links to begin to better understand some common process control industry general terminology.

Instrumentation Terms | Communication Terms | Control Terms | Process Variable Terms

Instrumentation Terms

Input – Something put into a system to achieve output or result.

Output – An amount produced by a program or process from specific inputs.

Screw Terminal – A connection means between equipment and wires.

Indicator – An index used to show state of operation or condition.

Data Logger – An equipment that stores date-time stamped information for later retrial.

Alarm – Mechanism to warn by means of a sound or signal.

Channels – An input or output means.

Operation – The act or process of operating or functioning. An action resulting from instructions.

Remote Operation – Control provided away from a near vicinity.

Display – To provide alpha numeric or graphic information.

Programmable – An ordered list of events to take place or procedures to be followed.

Totalizer – A process which performs accumulation.

Digital – Of or relating to a device that can read, write, or store information that is represented in numerical form.

Analog – A signal that represents continuously variable information.

Manual – Done by, used by, or operated with the hands, employing human rather than mechanical energy.

Multiplexer – A device that interleave more than one activity.

Pulse – A discrete change in voltage or current from a sensor that indicates the passage of an incremental amount.

RoHS compliant – A component is tested for the presence of Lead (Pb), Cadmium (Cd), Mercury (Hg), Hexavalent chromium (Hex-Cr), Polybrominated biphenyls (PBB), and Polybrominated diphenyl ethers (PBDE).

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Communication Terms

Communication – The technology employed in transmitting and receiving information.

RS-232 – communications, standard (Formerly “RS-232”) The most common asynchronous serial line standard. EIA-232 is the EIA equivalent of ITU-T V.24, and V.28. EIA-232 specifies the gender and pin use of connectors, but not their physical type. RS-423 specifies the electrical signals. 25-way D-type connectors are common but often only three wires are connected – one ground (pin 7) and one for data in each direction. The other pins are primarily related to hardware handshaking between sender and receiver and to carrier detection on modems.

RS-485 – communications, standard (Formerly “RS-485”) An EIA serial line standard which specifies 2-wire, half-duplex, differential line, multi-point communications. Maximum cable length is 1200m. Maximum data rates are 10Mbps at 1.2m or 100Kbps at 1200m. EIA-485 can implement multi-point communications network and specifies up to 32 drivers and 32 receivers on a single (2-wire) bus.

Modem – A device for passing digital data over telephone wires by modulating the data into an audio signal to send it and demodulating an audio signal into data to receive it.

Data – Factual information, especially information organized for analysis or used to reason or make decisions.

Data Logs – A collection of data points

Daisy Chain – A series of connected devices such as in a network.

Error Correction – A process which provides information integrity information about the base information.

Serial – Of or relating to sequential information transmission.

Management information System – A system designed to help managers plan and direct business and organizational operations.


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Control Terms

Control – A process or apparatus used to control a mechanism or machine operation.

PID – operating system (PID) A function used to facilitate closed loop control systems.

Dose – A specified quantity to be delivered at prescribed intervals.

Batch – A quantity to be delivered once in a single run.

Mix – To combine or blend into one mass or mixture.

Blending – To combine or mix so that the constituent parts are indistinguishable from one another, To combine (varieties or grades) to obtain a mixture of a particular character, quality, or consistency, To form a uniform mixture.

Mass flow control – A process that controls the rate of passage or amount of compressible masses which may be affected by pressure, temperature and other applicable constants and variables.

Embedded controller – A control device built into a host device.

Monitor – A device that accepts video signals from a computer and displays information on a screen; a video display. To compare a present value to preset limits.

Measure – Dimensions, quantity, or capacity as ascertained by comparison with a standard.

Rate – A quantity measured with respect to another measured quantity, such as time.

Smoothing Filter – A function that extracts the desired or required information from amongst other information.

Scalar – A quantity, such as mass, length, or speed, that is completely specified by its magnitude and has no direction, A number, numerical quantity, or element in a field, A device that yields an output equal to the input multiplied by a constant, as in a linear amplifier.

Tare – The weight of a container or wrapper that is deducted from the gross weight to obtain net weight., A deduction from gross weight made to allow for the weight of a container., A counterbalance, especially an empty vessel used to counterbalance the weight of a similar container.

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Process Variable Terms

Flow – To move or run smoothly with unbroken continuity, as in the manner characteristic of a fluid. , To proceed steadily and easily, the motion characteristic of fluids (liquids or gases) [syn: flowing] 2: the amount of fluid that flows in a given time [syn: flow rate, a rate of flow] 3: the act of flowing or streaming; continuous progression.

Pressure – The force applied to a unit area of surface.

Level – An elevation with respect to another elevation.

Temperature – The average kinetic energy of the particles in a sample of matter, expressed in terms of units or degrees designated on a standard scale.

Conductivity – A measure of transmission of heat or electricity or sound.

Resistance – A force that tends to oppose or retard motion, The opposition of a body or substance to current passing through it, resulting in a change of electrical energy into heat or another form of energy.

pH – The negative logarithm of the hydonium ion concentration in an aqueous solution.

ORP – Oxidation Reaction Potential.

TDS – Total Dissolved Solids.

Thermocouple – A thermoelectric device used to measure temperature consisting of two dissimilar metals joined so that a potential difference generated between the points of contact is a measure of the temperature difference between the points.

Reverse Osmosis – A method of producing pure water by forcing saline or impure water through a semi-permeable membrane across which salts or impurities cannot pass.

Turbidity – Having suspended sediment or foreign particles.