ABBREVIATIONS AND ACRONYMS FOR STANDARDS & STANDARDS BODIES

CALIBRATION

CONTROL

INSTRUMENTATION – GENERAL

THERMOMETRY – GENERAL

 

ABBREVIATIONS AND ACRONYMS FOR STANDARDS & STANDARDS BODIES

 

ANSI	American National Standards Institute
ASTM	American Society for Testing and Materials
BASEEFA	Health and Safety Executive Standard on Plant safety
BSI	British Standards Institution
BS	British Standards Institution Standards
CEN	European Committee for Standardisation
CENELEC	European Committee for Electrical Standardisation
DIN	Deutsche Institut fur Normung
ELSECOM	European Electrotechnical Sectoral Committee for Testing and Certification
EN	CEN/CENELEC European Standards
EOTC	European Organisation for Testing and Certification
GAMBICA	The Association for the Instrumentation, Control and Automation Industry in the UK.
IEC	International Electrotechnical Commission
IEEE	IEEE Standards
IPTS-68	International Practical Temperature Scale of 1968
ISO	International Organisation for Standardisation
ITS-90	International Temperature Scale of 1990
NAMAS	EEC listed Certification Bodies/Accreditation Service
NBS	National Bureau of Standards, USA
NPL	National Physical Laboratory, UK
UKAS	United Kingdom Accreditation Service

 

CALIBRATION

 

Calibration	Checking/ measuring accuracy against an external reference/standard
Calibrator	Device used for or in calibration
Drift	Change in the value of a parameter due to operational influence (e.g. temperature variation / ageing)
Dry Block Calibrator	A thermal device which does not use a fluid medium as a temperature source
Fixed Points (Temperature)	Temperatures defined by physical laws, change of state of pure materials
Fixed Point Cell	A device used to provide a fixed point temperature
Primary Standards	Those derived from the best available equipment. Pertaining to establishing the International Temperature Scale.
Reference Probe	Certified probe used as a comparison standard
Secondary Standard	Traceable to primary Standards
Simulator	Instrument which produces electrical signals emulating those of sensors
Standard Resistance Thermometer	A laboratory standard probe for the highest possible accuracy of measurement
Stirred Liquid Bath	A controlled thermal reference which uses a stirred liquid medium
Temperature	A temperature value at which calibration is performed by
Calibration Point	comparison or direct techniques
Thermal Calibration	Calibration using a temperature source (i.e. not electrical)
Thermal Reference	Controlled temperature source
Tolerances	Stated uncertainties
Triple Point of Water	A thermodynamic state (of water) in which the gas, liquid and solid phases all occur in equilibrium. Value 0.01°C
Uncertainties	Possible inaccuracies

 

CONTROL

 

Auto-manual	Selection of closed loop (automatic) or open loop (manual) regulation
Auto-tune	Automatic selection of the control terms, usually P,I and D
Bumpless Transfer process	Permits switching from manual to automatic control without disturbances due to integral saturation
Calibration	Checking/measuring accuracy against an external reference or standard
Closed Loop	Automatic control via feedback
Cold Junction Compensation (Automatic)	Built-in, automatic compensation for ambient temperature variations when using a thermocouple sensor
Controller	The instrument which provides automatic measurement and control of a process
Control Output	The means of controlling energy regulation in the process
D	Abbreviation of Derivative
Dead-band	On-Off hysteresis to prevent excessively rapid power switching
Derivative Time Constant	A measure of Derivative term sensitivity
Hysteresis	Dead-band defined in on-off switching
I	Abbreviation of Integral
Integral Time	Summation period for offset computation
Offset	Difference between set-point and resultant control point
On-Off	Power regulation by simple on-off switching (e.g. thermostat)
Open Loop	System not utilising feedback (i.e. not capable of automatic control)
Output	Control signal or communication data
Overshoot	The amount by which the process temperature exceeds set-point on start-up
P	Abbreviation of proportional
Process	The system being monitored or controlled
Process Variable	The parameter monitored or controlled
Proportional Band	The control band within which power is regulated between 0 and 100% usually express as a percentage of the overall temperature range
Set-point	Desired process temperature set by the operator
Start-up	Dynamic state of the process after switching on
Thermal Mass	Heat storage effect in the process
Three Term	Defines P,I and D control action
Tuning	Optimising P,I and D terms to achieve good control. Can be manual or automatic

 

INSTRUMENTATION – GENERAL

 

Alternating Current (ac)	Electric current which alternates in direction. The number of times the current changes direction in one second is called the frequency.
Amplifier	A device which produces a larger output signal than is applied at its input.
Analogue-to-digital (A-D) Converter	Converts an analogue signal (such as a voltage signal from a temperature sensor) into a digital signal suitable for input to a computer.
ASCII	American Standard Code for Information Interchange. Coding for text files.
Batch Process	Any process on which operations are carried out on a limited number of items as opposed to continuous process.
CE	Conformite Europeene. A mark that is affixed to a product to designate that it is in full compliance with all applicable European Union legal requirements.
Closed Loop	Facility for automatic control by means of temperature feedback from the process to the instrument
Common-Mode Signal	A signal applied simultaneously to both inputs of a device.
Common-Mode Rejection Ratio (cmrr)	The ability of the device to obtain the difference between the + and – inputs whilst rejecting the signal common to both.
Comms	Abbreviation of Communications interface
Contact emf	Electromotive force which arises at the point of contact metals.
Control	Regulation of process energy to achieve a desired temperature
Data Acquisition	Gathering data from a process, usually electronic, usually automatic
DAU	Abbreviation of Data Acquisition Unit
Direct Current (dc)	Current which flows in one direction.
Electromotive Force (emf)	Difference of potential (V) produced by sources of electrical energy which can be used to drive currents through external circuits.
Excitation	The operational voltage or current applied to a transducer.
Filtering	Attenuates components of undesired signal
Frequency	Measured in Hertz (cycles per second), rate of repetition of changes.
Full Scale Output	The difference between the minimum output (normally zero) of a device and the rated capacity (full signal).
Gain	Amplification of a circuit.
Ground	Connection to ground (earth).
HART	Highway Addressable Remote Terminal. Provides digital communication to microprocessor-based (smart) analogue process control instruments.
Hertz (Hz)	Cycles per second unit of frequency.
Indication	Analogue or digital readout of data
Input	The connection point for a sensor or defines type of sensor
I/O	Input/Output. A measuring system monitors signal through its inputs and sends control signals through its outputs.
Isolation	Electrically isolated condition
Linearisation	Matching the transfer characteristic of the sensor if non­linear (strictly de-linearisation)
Logging	Recording data
Noise	Any unwanted electrical signals affecting the signal to be measured.
Non-linear	Not a straight line transfer characteristic
Open Loop	System not utilising feedback
Output	Data exiting a device
PC	Personal Computer. Generally applied to computers conforming to the IBM designed architecture.
Pick-up	Superimposition of unwanted electrical signals in the system (usually high frequency and/or high voltage)
PID	Proportional gain, integral action time and derivative action time.
Port	The external connector of a device.
Positive Temperature Coefficient	An increase in resistance due to an increase in temperature.
Process	The system being monitored
Protocol	A set of rules used in data communications.
QA	Quality Assurance
Range	Full-scale signal (input or output).
Relay	Electromechanical device that opens or closes contacts when a current is passed through its coil.
Resolution	A measure of the smallest detectable change.
Repeatability	The ability of an instrument to repeatedly give the same reading.
r.f.i.	Abbreviation of radio frequency interference
SCADA	Abbreviation of Supervisory Control and Analogue Data Acquisition
Scan	Reading each input channel in turn. The scan will return to the first channel once all the channels have been sampled.
Seebeck Effect	The thermocouple principle. In a circuit in which there are junctions between dissimilar metals, an electromotive force (voltage) is set up when the junctions are at different temperatures.
Sensitivity	A measure of the minimum change in an input signal that an instrument can detect.
Sensor	A device that can detect a change in a physical quantity and produce a corresponding electrical signal.
Serial Communication	Where data is transferred one bit at a time.
Settling Time	When a change in signal occurs, the time taken for the input or output channel to settle to its new value.
SI	International system of units. Abbreviation for Systeme International (d’Unites).
Signal Conditioning	Changing the electrical characteristics of a sensor signal
Stability	The ability of an instrument to maintain a consistent output with the application of a constant input
System	Combination of several circuits or items of equipment to perform in a particular manner.
Temperature	Amount by which a parameter varies due to temperature Coefficient of...
Thermal Conductivity	A measure of the rate of flow of thermal energy through a material in the presence of a temperature gradient. Materials with high electrical conductivities usually have high thermal conductivities.
Transient	A short duration surge of current or voltage.
Transmitter	A device for amplifying a sensor signal in order to permit its transmission to remote instrumentation. Usually converts to 4-20mA

 

THERMOMETRY – GENERAL

 

Absolute Zero	The lowest possible temperature of a body due to absence of molecular motion. Stated as 0 Kelvin, equivalent to - 273.15°C
Alpha	The temperature coefficient of resistance of a sensing resistor. Expressed as W/°C
Alumina	Aluminium Oxide (a refractory material)
Barrier Terminal	Terminal block configuration
Base Metal Thermocouple	Thermocouple utilising base metals
Boiling Point	The equilibrium temperature between a liquid and its vapour
Callendar – Van Dusen Equation	An interpolation equation which provides resistance values as a function of temperature for sensing resistors
Ceramic	Refractory insulating material
Coefficients (ABC)	Used in the Pt100 characteristic polynomial; they define the temperature – resistance relationship
Cold junction	Reference junction of a thermocouple
Cold Junction Compensation (CJC)	Compensation for thermocouple reference junction temperature variations
Colour Codes	Means of cable and sensor type identification; applied internationally according to appropriate standards
Compensating Cable	Used for connecting thermocouples to instruments; the conductors use low cost materials which have a similar ambient thermal emf relationship to that of the thermoelement but at lower cost
Compression Fitting	Type of threaded fitting which compresses on to the probe sheath to provide a pressure tight coupling
Cryogenic	A term for very low temperatures, usually associated with liquified gases
Drift	Change in the value of a parameter due to operational influence (e.g. temperature variation / ageing)
Excitation Current	Current supplied to an appropriate sensor or transducer to provide excitation
Exposed Junction	A thermojunction not protected by sheath material. Used when fast thermal response is required
Extension Cable	Thermocouple connecting cable which uses conductors in true thermocouple alloy
Fabricated	Made from component parts e.g. a thermocouple assembly made from tubing, wire and insulating materials as opposed to one made using mineral insulated cable
Fittings	Items used to secure probes into machinery e.g. compression glands, threaded bushes, bayonet fittings
Fixed Points (Temperature)	Temperatures defined by physical laws, change of state of pure materials
Flange	Form of disc through which probe is installed into a process
Freezing Point	The fixed temperature point of a material which occurs during the transition from a liquid to solid state. Also known as Melting Point for pure materials.
Fundamental	Thermometer resistance change over the range 0 to 100°C Interval
Grounded Hot Junction	Thermocouple configuration in which the thermoelement is electrically common to the sheath
Hot Junction	Measuring junction of thermocouple
Ice Point	0°C
Immersion	Placing of probe into the process medium (i.e. immersion into some medium)
Insert	Replaceable probe assembly located inside outer sheath
Insulation Resistance	Value of resistance measured between the sensor wire and sheath
Interchangeability	Describes how closely a sensor adheres to its defining equation
Isothermal	Equal temperature
Lagging Extension	Probe or pocket extension to allow for thickness of pipe or wall lagging
Leg	Common term for one thermoelement wire in a thermocouple circuit
Linearity	A deviation in response from straight line value of a sensor
Loop Resistance	The total resistance of a thermocouple circuit
Measuring Junction	Thermoelement measuring junction (hot junction)
Melting Point	The temperature at which a substance converts from the solid to liquid phases. This is the same as the Freezing Point for pure materials
Metallic	Pertaining to presence of metal in sheath material as opposed to non-metallic
MI	Abbreviation for Mineral Insulated as used in sensor cable
Mineral Insulated	Type of cable construction used in thermometry. Conductors are insulated from sheath by compressed refractory oxide powder.
Noble Metal t/c	Rare metal, usually Platinum / Rhodium alloys
Noise	Unwanted electrical interference picked up on a signal cable
NTC	Negative temperature coefficient (of resistance)
Parallel Pair	Wire construction where two single conductors are laid parallel
Platinum Resistance (PRT) temperature	Platinum temperature sensor whose resistance varies with Thermometer
Polarity	Determines the direction of current flow in an electrical circuit
Protection Tube	A tube (sheath) which protects a sensor from its operating environment
PTC	Positive temperature coefficient (of resistance)
Rare Metal t/c	Thermocouple made of rare metal thermoelement
Reference Junction	Of the thermocouple, usually referred to the ice point
Resistance	Temperature sensor, usually Platinum, whose resistance varies with Thermometer temperature
Response Time	A measure of thermal sensitivity applied to sensors. The time required for a sensor to reach 63% of the step change in temperature under particular conditions
Ro	The value of thermometer resistance temperature sensors at 0°C
RTD	Abbreviation for resistance temperature detector
Self-heating	Heating effect due to current flow in the sensing resistor of a resistance thermometer
Sensing Length	That portion of the probe sensitive to temperature
Sensing Resistor	The sensing element of a resistance thermometer
Stability	The ability of a sensor to maintain a consistant output with the application of a constant input
Stem Conduction	The flow of heat away from the sensing length of a probe due to probe thermal conductivity
Stem Sensing	Sensing over a finite length of sheath as opposed to just the tip
Tails	Connecting wires emanating from the sensor
Thermal Gradient	The distribution of different temperatures in and across an object
Thermal Mass	Heat storage effect in the process
Thermistor	A form of resistance thermometer, usually a NTC type.
Thermocouple	Temperature sensor based on a thermoelement
Thermocouple Type	Defines the type of thermoelement e.g. J,K,T,E,N,R,S,B etc.
Thermoelectric	Electrical activity resulting from the generation of thermo-voltages
Thermoelement	The two dissimilar conductors and their junction forming a thermocouple
Thermojunction	The junction formed between the dissimilar conductors of a thermocouple. Usually describes the measuring junction
Thermowell	Used to protect sensor probes against aggressive media. Effectively a pocket or well in the process into which the probe is inserted
Thin Film	Sensing resistor in a thin film form
Tip Sensing	Temperature sensing at the tip of a probe only as opposed to along its length
Transducer	A device which converts energy from one form into another. Transducer often describes a sensor
Transfer Function	Input/Output characteristic of a device
Transmitter	A device for amplifying a sensor signal in order to permit its transmission to remote instrumentation. Usually converts to 4-20mA
Twisted Pair	Two insulated conductors twisted together. Twisted wires in thermocouple circuits minimise noise pick-up
Wheatstone Bridge	A network of four resistances, an emf voltage source, and an indicator connected such that when the four resistances are matched, the indicator will show a zero deflection or “null” reading. Prototype of most other bridge circuits.
Wirewound	Sensing resistor in wirewound construction

 

 

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