Note:  Do not rely on this information. It is very old.


Calibration of an instrument means the determination of the meaning of its readings. A galvanometer needle may be deflected 30° by an electrical current passing through the instrument; its calibration enables us to specify what is the measure of this current. If the measure is expressed absolutely, in amperes or other definite units, the calibration is called absolute. If only the comparison of the magnitudes of the currents that will produce definite effects is afforded, the calibration is termed relative. It is of considerable importance in most physical measuring instruments.