A wide-range volt-ampere converter for current and voltage measurements

Technological developments have brought increasing needs for convenient, portable instruments for measuring current and voltage with high accuracy over a wide range of frequencies. A “universal” volt-ampere (VA) converter has been developed for making such measurements to 0.05% with alternating current at frequencies from 5 cps (cycles per second) to 50 kc and with direct current. The new model is based on an earlier, much more limited prototype converter,1 and, like it, is used with a null-type d-c potentiometer. With this single, self-contained, portable, 44-range instrument, the 1.5-volt range of a suitable potentiometer can be used to make a-c (rms) and d-c measurements from 7.5 milliamperes (ma) to 20 amperes and from 0.5 volt to 600 volts. With a more sensitive external galvanometer, the instrument can also be used as an a-c-d-c transfer standard for a-c-d-c difference measurements to 0.02% over the same frequency range.