Apparatus having a wheatstone bridge circuit for testing continuity and leakage in electric cables

Claim 1

APPARATUS FOR TESTING THE CONTINUITY AND LEAKAGE IN ELECTRIC CABLE CONDUCTORS COMPRISING A WHEATSTONE BRIDGE HAVING A FIRST, SECOND, THIRD AND FOURTH LEGS CONNECTED IN SERIES ONE WITH THE OTHERS TO FORM FOUR INTERMEDIATE JUNCTIONS, EACH OF SAID LEGS INCLUDING AT LEAST ONE IMPEDANCE, VARIABLE IMPEDANCE MEANS IN SERIES WITH AT LEAST ONE OF SAID LEG IMPEDANCES FOR BALANCING SAID BRIDGE, MEANS CONNECTED WITH ONE PAIR OF OPPOSING JUNCTIONS FORMED BY THE CONNECTION OF THE FIRST AND THIRD LEGS AND BY THE JUNCTION OF THE SECOND AND FOURTH LEGS FOR ENERGIZING SAID BRIDGE, A COMMON GROUND, A PLUARLITY OF SCALE FACTOR IMPEDANCES, FIRST SWITCH MEANS INTERCONNECTED WITH SAID SCALE FACTOR IMPEDANCES, GROUND AND THE IMPEDANCE IN SAID FOURTH LEG TO SELECTIVELY INTRODUCE SAID SCALE FACTOR IMPEDANCES IN SERIES BETWEEN GROUND AND SAID FOURTH LEG IMPEDANCE, SECOND MULTI-POSITION SWITCH MEANS INTERCONNECTED WITH SAID THIRD LEG IMPEDANCE AND HAVING A TERMINAL FOR CONNECTION OF A CABLE CONDUCTOR TO BE TESTED AND A TERMINAL CONNECTED TO GROUND, THE LAST SAID SWITCH MEANS IN ONE POSITION CONNECTING SAID CABLE CONDUCTOR IN SERIES BETWEEN THE IMPEDANCE OF SAID THIRD LEG AND GROUND AND IN ANOTHER POSITION CONNECTING THE IMPEDANCE OF SAID THIRD LEG DIRECTLY TO GROUND, SAID GROUND CONSTITUTING THE JUNCTION BETWEEN THE IMPEDANCCES IN SAID THIRD AND FOURTH LEGS, A THIRD MULTI-POSITION SWITCH, AN A.C. AMPLIFIER, A CONNECTION BETWEEN SAID AMPLIFIER AND SAID THIRD SWITCH MEANS NECTION BETWEEN SAID AMPLIFIER AND SAID THIRD SWITCH MEANS AND A CONNECTION BETWEEN SAID THIRD SWITCH MEANS AND THE JUNCTION BETWEEN SAID FIRST AND SECOND LEGS OF SAID BRIDGE, SAID THIRD SWITCH BEING OPERABLE IN ONE POSITION TO FEED AN OUTPUT SIGNAL FROM SAID BRIDGE TO SAID AMPLIFIER, INDICATING MEANS CONNECTED TO SAID AMPLIFIER FOR INDICATING THE MAGNITUDE OF SAID AMPLIFIED BRIDGE VOLTAGE, A SOURCE OF HIGH VOLTAGE, A PAIR OF TERMINAL MEANS FOR ATTACHMENT OF A PAIR OF CONDUCTORS OF A CABLE TO TEST LEAKAGE THEREBETWEEN, A CONNECTION BETWEEN ONE OF SAID TERMINALS AND ONE SIDE OF SAID HIGH VOLTAGE SOURCE, A LOAD IMPEDANCE, A PLURALITY OF RESISTORS, CONNECTIONS BETWEEN ONE END OF EACH OF SAID RESISTORS AND THE OTHER OF SAID TERMINALS, FOURTH MULTI-POSITION SWITCH MEANS CONNECTED TO THE OTHER ENDS OF SAID RESISTORS AND TO ONE SIDE OF SAID LOAD IMPEDANCE, A CONNECTION BETWEEN THE OTHER SIDE OF SAID LOAD IMPEDANCE AND GROUND, A CONNECTION BETWEEN, THE OTHER SIDE OF SAID HIGH VOLTAGE SOURCE AND GROUND, SAID FOURTH SWITCH MEANS SELECTIVELY PLACING SAID RESISTORS IN SERIES WITH SAID LOAD IMPEDANCE, A CHOPPER HAVING AN INPUT CONNECTED TO SAID LOAD IMPEDANCE AND PRODUCING AN INTERRUPTED OUTPUT VOLTAGE HAVING A PEAK VALUE SUBSTANTIALLY EQUAL TO THE VOLTAGE HAVING A PEAK VALUE SUBTRICAL CONNECTION BETWEEN THE OUTPUT OF SAID CHOPPER AND SAID THIRD SWITCH MEANS WHEREBY SAID THIRD SWITCH IN ANOTHER POSITION FEEDS SAID INTERRUPTED VOLTAGE TO SAID AMPLIFIER, AND A MAGNETIC COUPLING BETWEEN SAID SECOND AND THIRD SWITCH MEANS FOR SIMULTANEOUSLY OPERATING SAID SWITCHES TO SELECTIVELY CONNECT SAID BRIDGE AND CHOPPER SIGNALS TO SAID INDICATING MEANS.