A novel alternating-current voltmeter

This paper describes an improved thermo-voltmeter, which may be used at all frequencies up to and including 1,000,000 cycles. This meter retains the usual high sensitivity of thermovoltmeters so that it requires a very small current — for full scale deflection about 2 milliamperes. At present it is made in ranges from 1 to 20 volts inclusive. Higher voltage ranges can be made but probably at the expense of lowering somewhat the upper limit of frequency at which the instrument is still accurate.