Portable insulation testing equipment adaptable for conversion from straight to inverted schering-bridge operation

Claim 1

A PORTABLE TESTING DEVICE FOR MEASURING THE POWER FACTOR AND CAPACITANCE OF A GROUNDED OR UNGROUNDED INSULATING SPECIMEN COMPRISING, IN COMBINATION, A SCHERING-BRIDGE CIRCUIT INCLUDING ADJUSTABLE IMPEDANCES, CONNECTED IN FIRST AND SECOND ARMS OF THE BRIDGE CIRCUIT AND JOINED AT A FIRST JUNCTION POINT, A CURRENT-BALANCE INDICATOR, SAID BRIDGE CIRUCIT HAVING A CONDENSER OF FIXED CAPACITY IN THE THIRD ARM THEREOF, SAID BRIDGE CIRCUIT HAVING CABLECONNECTING MEANS FOR CONNECTING THE INSULATING SPECIMEN IN THE FOURTH ARM THEREOF, SAID THIRD AND FOURTH ARMS OF THE BRIDGE CIRCUIT MEETING AT A SECOND JUNCTION POINT, A HIGH-VOLTAGE SOURCE FOR IMPRESSING HIGH TESTING VOLTAGE ACROSS THE FIRST AND SECOND JUNCTION POINTS, MEANS INCLUDING A CONTROL PANEL FOR ADJUSTING SAID ADJUSTABLE IMPEDANCES FOR BALANCING THE BRIDGE CIRCUIT SO THAT NO CURRENT WILL FLOW THROUGH THE CURRENT-BALANCE INDICATOR, A METALLIC SHIELDING CASING ENCLOSING SAID FIRST AND SECOND BRIDGE ARMS TOGETHER WITH THE CURRENT-BALANCE INDICATOR AND ELECTRICALLY CONNECTED TO SAID FIRST JUNCTION POINT, SAID CONDENSER OF FIXED CAPACITY HAVING HIGH- AND LOWVOLTAGE ELECTRODE PLATES, TWO-POSITIONAL CONVERSION SWITCHING MEANS FOR ADAPTING THE TESTING DEVICE ALTERNATIVELY FROM STRAIGHT TO INVERTED SCHERING-BRIDGE OPERATION, THE FIRST POSITION OF SAID CONVERSION SWITCHING MEANS CONNECTING HIGH-TESTING VOLTAGE FROM SAID HIGH-VOLTAGE SOURCE TO THE HIGH-VOLTAGE ELECTRODE PLATES OF THE FIXED-CAPACITY CONDENSER AND ALSO CONNECTING THE LOW-VOLTAGE PLATES OF SAID CONDENSER TO THE CURRENT-BALANCE INDICATOR, THE SECOND POSITION OF SAID TWO-POSITIONAL CONVERSION SWITCHING MEANS CONNECTING HIGH TESTING VOLTAGE FROM SAID HIGHVOLTAGE SOURCE TO SAID FIRST JUNCTION POINT AND THE LOWVOLTAGE ELECTRODE PLATES OF THE FIXED-CAPACITY CONDENSER TO GROUND, AND MEANS FOR GROUNDING SAID METALLIC SHEILDING CASING IN THE FIRST POSITION OF THE TWO-POSITIONAL CONVERSION SWITCHING MEANS.