Electrical apparatus for testing joints having four voltage probes

Claim 1

TEST APPARATUS FOR TESTING THE CONDITION OF A JOINT FORMED BETWEEN A PAIR OF ELECTRICAL CONDUCTORS, COMPRISING, A SOURCE OF ALTERNATING POTENTIAL, MEANS FOR ADJUSTING THE MAGNITUDE OF SAID SOURCE OF ALTERNATING POTENTIAL. SAID SOURCE OF ALTERNATING POTENTIAL BEING ADAPTED FOR CONNECTION ACROSS THE JOINT TO BE TESTED, FIRST AND SECOND PAIR OF CONTACT MEMBERS, THE CONTACT MEMBERS OF EACH OF SAID FIRST AND SECOND PAIR BEING SPACED A PREDETERMINED DISTANCE APART, ONE OF SAID PAIR OF CONTACT MEMBERS BEING ADAPTED FOR CONNECTION TO ONE OF THE PAIR OF ELECTRICAL CONDUCTORS, THE REMAINING PAIR OF CONTACT MEMBERS BEING ADAPTED FOR CONNECTION ACROSS THE JOINT BETWEEN THE PAIR OF ELECTRICAL CONDUCTORS, A TRANSFORMER HAVING FIRST AND SECOND INPUT WINDINGS ARRANGED IN OPPOSITION, AND AN OUTPUT WINDING, SAID FIRST AND SECOND PAIR OF CONTACT MEMBERS BEING CONNECTED TO SAID FIRST AND SECOND INPUT WINDINGS, RESPECTIVELY, AND INDICATING MEANS CONNECTED TO THE OUTPUT WINDING OF SAID TRANSFORMER, SAID OUTPUT WINDING APPLYING A SIGNAL TO SAID INDICATING MEANS RESPONSIVE TO THE DIFFERENCE BETWEEN THE SIGNALS APPLIED TO SAID FIRST AND SECOND INPUT WINDINGS BY SAID FIRST AND SECOND PAIR OF CONTACT MEMBERS.