Process measurement calibration: Why? What? When? How? Who?

The advantages of using effective calibration in a measurement system are discussed. A measurement suffers two component types of error, namely, an error component and a systematic error component. An error component will vary between repeated measurements of the same variable made under the same circumstances while a systematic error is fixed for repeated measurements of the same variable made under the same circumstances. The random error is determined by the measurement device/system design and its intrinsic capability, and will remain unaffected by calibration. It will tend to worsen as a measurement system deteriorates through damage, wear or ageing. Calibration is used to detect random errors and identify a deteriorating system and it can reveal and correct drift in the measurement systems. It is necessary that the calibration standards should be more accurate than the device being calibrated or the calibration may degrade performance.