In calibration, the relationship between the measured value of an output quantity and the corresponding value of the measured input quantity is determined under specified conditions. Simply put: comparison with a reference having the same units, which in measurement engineering means determining the measurement deviation returned by measurement equipment. Calibration does not entail technical intervention – such as adjustment – in the measurement equipment. With indicator measurement equipment, calibration determines the deviation between the measured value indicated and the correct value – or the reference value considered correct.
Calibrations are performed in order to ensure that the measurement equipment used indicates values having a known and documented proportionality to an internationally accepted standard for the quantity measured. The goal is that when measurements of the same quantities are performed by different parties, e.g., customer and supplier, comparable results are obtained. The prerequisite for this is that the measurement uncertainty—which is inherent in any measurement—must be known.
Performing calibration leads to results and findings which provide a guide in better understanding and assessing the tolerances of measurement equipment.