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Control and Instrumentation Glossary

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Radio Frequency
The frequency range between ultrasonic and infrared.

Further Reading


RAL Number
The RAL catalogue is an international color standard that defines colours according to numbers and names e.g. RAL7032 is a flinty grey colour.

Further Reading


The region between the limits within which a quantity is measured; received or transmitted expressed by stating lower and upper range values.

Further Reading


The existence of more than one piece of equipment any of which could perform a given function.
These multiple pieces of equipment are used to help improve the reliability and availability of the system.
Further Reading


A quantitive measure of the variability associated in obtaining succesive repeat results from the same instrument in the same location under similar conditions.

Further Reading


The closeness of agreement among repeated measurements of an output for the same value of input made under the same operating conditions over a period of time.

Further Reading


The smallest change in input which produces a detectable change in output i.e. the smallest increment of change that can be detected by a measurement system.

Further Reading


A condition of oscillation caused when a small amplitude of periodic input has a frequency approaching one of the natural frequencies of the driven system.

Further Reading


Response Time
An output expressed as a function of time.
Common to use T90, i.e. time to achieve 90% of output.
Further Reading


Raised Face
Description of the mating face of a flange.
Further Reading


RFI - Radio Frequency Interference
Noise induced upon signal wires by ambient radio-frequency electromagnetic radiation with the effect of obscuring an instrument signal.

Further Reading


RH - Relative Humidity
An expression of the level of water vapour present compared to the maximum amount of water vapour that a gas could carry at that temperature.
It is expressed in percentage terms.
Further Reading


RTD - Resistance Temperature Detector
Resistance Temperature Detectors (RTD's) provide temperature measurement through changes in electrical resistance.

Further Reading


RTJ - Ring Type Joint
Description of the mating face of a flange where the mating face has a machined groove into which the gasket is inserted.

Further Reading


Remote Telemetry Unit

Further Reading


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