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Radio Frequency
The frequency range between ultrasonic and infrared.

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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.

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

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

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Reproducibility
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.

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Resolution
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.

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Resonance
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.

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

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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

 


RTU
Remote Telemetry Unit

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