Accuracy of Alternating-Current Test Instruments
S. C. Hoare · Transactions of the American Institute of Electrical Engineers · 1925
The paper deals mainly with the accuracy of instruments used under maintained conditions of load. Well designed voltmeters, ammeters, and wattmeters show very small errors due to self-heating and changes in ambient temperatures. Iron-vane ammeters are described which have small errors due to direct-current hysteresis and changes in wave-forms.