(a) Frequency error
(b) Temperature error (a) Frequency error Since deflecting torque depends on frequency, hence unless the alternating current to be measured has the same frequency with which the instrument was calibrated, there will be large error in its readings. Frequency errors can be compensated for by the use of a non-inductive shunt in the case of ammeters. In voltmeters, such errors are nor large and, to a great extent, are self-compensating. (b) Temperature error Serious errors may occur due to the variation of temperature because the resistances of eddy current paths depend on the temperature. Such errors can, however, be compensated for by shunting in the case of ammeters and by a combination of shunt and swamping resistance in the case of voltmeters.
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