calibration -
the act of checking or adjusting (by comparison with a standard) the accuracy of a measuring instrument; "the thermometer needed calibration"
Calibration is a comparison between measurements - one of known magnitude or correctness made or set with one device and another measurement made in as similar a way as possible with a second device. The device with the known or assigned correctness is called the standard. The second device is the unit under test (UUT), test instrument (TI), or any of several other names for the device being calibrated.
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calibration The marking the scale of a measuring instrument so that readings can be made in appropriate units.