Calibration of Voltmeters

Calibration of Voltmeters Points : Calibration of Voltmeters, D.C. Calibration, AC. Calibration Main types of calibration are
1. D.C. Calibration.
2. AC. Calibration. 1. D.C. Calibration: There are two methods of D.C. Calibration:
(i) Comparison with standard voltmeter
(ii) By d.c. potentiometer (i) Comparison with standard Voltmeter The test voltmeter and standard voltmeter are connected in parallel to a variable direct voltage source and the readings of the test voltmeter are checked directly against those of the standard. (ii) By dc. Potentiometer The test instrument is connected across a variable direct voltage source; the p.d. across the instrument is measured by the potentiometer, a volt ratio-box being used when necessary. 2. A.C. Calibration Following four methods are used for a.c. calibration of voltmeters
(i) By standard voltmeter
(ii) By ac. potentiometer
(iii) By electrostatic voltmeter
(iv) By d.c. calibration These methods are similar to those described for ammeters; except that variable voltage, rather than current, is required from the source, the test instrument is placed in parallel with any standard instrument, and a volt ratio-box (not a shunt) is required with the potentiometer.