A thermionic voltmeter with a linear law
D G Reid · Journal of Scientific Instruments · 1938
An A.C. mains operated direct-reading voltmeter is described, the voltage range extending from 0.1 to 1.0 V., higher ranges being available by means of an input divider circuit. Frequency error is negligible up to about 1.5 MC.P.S. The meter is subject to wave-form error.