Calibration of Instruments

It is presumed that most instruments exhibit linearity in the range of their operation. An instrument is said to be linear if the input physical quantity and the resulting output reading of the instrument have a linear relationship. The output of the instrument could be linear deflection, angular deflection or voltage etc. This output has to be displayed in terms of the physical quantity which the instrument was expected to measure in the first place. The manufacturer calibrates this display by comparing the output of the instrument with respect to a standard input. Having obtained such an instrument, which has been marked and calibrated by the manufacturer, the user has to periodically calibrate the instrument to see whether it is working within the prescribed limits.