A tuned detector-amplifier for power-frequency measurements
W K Clothier, W E Smith · Journal of Scientific Instruments · 1955
A tuned detector-amplifier for power frequencies (20-60 c/s) is described. It can detect ¼ μV in a 1 MΩ resistance source and when used with suitable tuned input transformers, its power sensitivity is 10 -19 W. The amplifier is tuned by means of a two-section inductance-capacitance filter, the inductors of which are varied simultaneously by a direct current in control windings on their Mumetal cores.