Method and apparatus for measuring impedance increases in the ground or protective ground wires leading to three-wire prong power receptacles

Claim 1

APPARATUS FOR TREATING ALTERNATING-CURRENT RECEPTACLES OF THE TYPE INCLUDING POWER LINE, NEUTRAL AND PROTECTIVE GROUND TERMINALS, COMPRISING PLUG MEANS INCLUDING LINE, NEUTRAL AND PROTECTIVE GROUND CONTACTS ADAPTED FOR ELECTRICAL ENGAGEMENT WITH THE LINE, NEUTRAL AND PROTECTIVE GROUND TERMINALS OF THE RECEPTACLE, RESPECTIVELY; A VOLTMETER HAVING FIRST AND SECOND TERMINALS; A NEON LIGHT; A CURRENT LIMITING RESISTOR CONNECTED IN SERIES WITH SAID NEON LIGHT TO DEFINE A SERIES BRANCH; AN IMPEDANCE LOAD CONNECTED ACROSS THE ENDS OF SAID SERIES BRANCH TO DEFINE A PARALLEL NETWORK; MEANS INCLUDING A NORMALLY OPEN FIRST MANUAL SWITCH OPERABLE TO CONNECT SAID PARALLEL NETWORK ACROSS THE FIRST AND SECOND TERMINALS OF SAID VOLTMETER; FIRST CONDUCTOR MEANS CONNECTING THE FIRST TERMINAL OF SAID VOLTMETER WITH THE LINE CONTACT OF SAID PLUG MEANS; AND MEANS INCLUDING A SECOND MANUAL SWITCH FOR CONNECTING THE SECOND TERMINAL OF SAID VOLTMETER ALTERNATELY WITH THE NEUTRAL AND PROTECTIVE GROUND CONTACTS OF SAID PLUG MEANS, RESPECTIVELY.