Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, a device generating the quantity to be measured such as a voltage, sound tone, or a physical artefact, such as a metre ruler.

The outcome of the comparison can result in no significant error being noted on the device under test, a significant error being noted but no adjustment made, or an adjustment made to correct the error to an acceptable level. Strictly speaking, the term calibration means just the act of comparison, and does not include any subsequent adjustment.

Calibration may be required for the following reasons:

a new instrument
after an instrument has been repaired or modified
when a specified time period has elapsed
when a specified usage (operating hours) has elapsed
before and/or after a critical measurement
after an event, for example after an instrument has been exposed to a shock, vibration, or physical damage, which might potentially have compromised the integrity of its calibration or with sudden changes in weather
whenever observations appear questionable or instrument indications do not match the output of surrogate instruments
as specified by a requirement, e.g., customer specification, instrument manufacturer recommendation.

Coming soon – a directory of resources relating to the supply of Calibrators and Calibration equipment in South Africa