A calibration service is a service aimed at detecting the inaccuracy and uncertainty of a measuring instrument or piece of equipment. In calibration, the device under test (DUT) is compared to a reference of known value to determine the deviation of the measurement from the true value. Deviation of the actual value from the measured value is called an error. After the error has been detected, the next move is to adjust the DUT to obtain more accurate measurements, but this is a separate process called adjusting or trimming.