AC_LINE_POLARITY_METER

Published:2009/7/15 20:29:00 Author:Jessie | From:SeekIC

Used to determine correctness of ground wiring in receptacle. Circuit compares voltage waveform on line conductors with AC potential of 10-40 V at 60 Hz picked up by antenna which can be human body. Circuit is synchronous demodulator that conducts on alternate half-cycles depending on whether gate voltage of JFET is positive with respect to source or drain. Zero-center DC milliammeter serves as readout. If plug is inserted into receptacle having balanced power line, milliammetet stays at center to indicate lack of ground. With properly grounded receptacle, meter swings full scale in either direction.-T. Gross, Indicator Shows Correct Wiring Polarity, EDN Magazine, Oct. 20, 1978, p 150 and 152.



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