The measurement of the mean value of a current
G.W. Bowdler · Journal of Scientific Instruments · 1930
Two null methods of measuring the mean value of a current are described, and the precautions to be observed in each case are examined. Finally the two methods are simultaneously applied to the measurement of rectified alternating current, the frequency of which is varied between 50 and 4000 cycles per second. The results obtained by the two methods agree in every case to a few parts in 10,000. Calibration of a permanent magnet moving-coil ammeter by these two methods indicates that no appreciable error arises when instruments of this type are used to measure rectified alternating current, whose frequency lies within the above mentioned range.