→ Calibrate a single phase energy meter by phantom loading at different power factor by Phase shifting transformer and Auto transformer.
Calibration of all instruments is important once it affords the opportunity to check the instrument against a known standard and to find error and accuracy. Polyphase or 3-phase energy meters in a ‘n’ conductors system requires (n-1) measuring elements for measurement of total energy. Thus a 3-phase 4 wire system requires a 3 element energy system. Polyphase energy meters may be multidisc type each element divides a separate disc. In the single disc type meter all elements drive the same disc.
The Q-meter is an instrument designed for the measurement of Q-factor of the coil as well as for the measurement of electrical properties of coils and capacitors. -This instrument operates on the principle of series resonance i.e. at resonate condition of an ac series circuit voltage across the capacitor is equal to the applied voltage times of Q of the circuit. If the voltage applied across the circuit is kept-constant then voltmeter connected across the capacitor can be calibrated to indicate Q directly.
If a metal wire or conductor is stretched or compressed its resistance changes because of change in length, change in resistivity and change in cross sectional area. This effect is called piezoresistive effect. The cantilever used in the primary elastic transducer of force measuring system, where a known mass is attached to cantilever, the unbalanced voltage, can be calibrated in terms of either force or weight.
The calibration is the process for determining the correct values of mesurand by compared with the standard ones. The potentiometer is extensively used for a calibration of voltmeter and ammeter .The procedure for standardization of the potentiometer is illustrated by the following example.