Alternate Current Measurement


THE ordinary dynamometer is as well adapted for direct as for alternate current measurements; but while it is generally regarded as the best available instrument for alternate currents, its use with direct currents is almost restricted to standard instruments of the ampere balance type. This is due to the immensely greater sensitiveness obtainable with direct current instruments constructed on the heterostatic principle, as exemplified in galvanometers with permanently magnetised needles or magnets. The latter instruments, due originally to Kelvin and Maxwell, and first developed commercially by Ayrton and Perry, have been brought to a high state of perfection in recent years, with the result that ordinary measurements on direct current circuits are much more precise and satisfactory than those on alternate current circuits.

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SUMPNER, W. Alternate Current Measurement . Nature 78, 88–89 (1908).

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