Apparatus including an automatic balancing bridge for measuring the temperature of motor windings and the like, including thermaly controlled ballast resistance means

Claim 1

RESISTANCE-CHANGE TEMPERATURE-MEASURING APPARATUS FOR AN ELECTRICALLY CONDUCTIVE DEVICE COMPRISING A SOURCE OF ENERGY FOR SUPPLYING CURRENT TO SAID DEVICE, MEANS FOR MEASURING THE RESISTANCE OF SAID DEVICE INCLUDING A RESISTANCE BRIDGE CIRCUIT, A BALLAST RESISTANCE NORMALLY CONNECTED INTO SAID BRIDGE CIRCUIT, THERMOSTATIC SWITCH MEANS RESPONSIVE TO THE TEMPERATURE OF SAID DEVICE FOR INTERRUPTING THE SUPPLY OF CURRENT TO SAID DEVICE AND CONNECTING SAID DEVICE INTO SAID RESISTANCE BRIDGE CIRCUIT IN PLACE OF SAID BALLAST RESISTANCE WHENEVER THE TEMPERATURE OF SAID DEVICE EXCEEDS A PRESELECTED LEVEL, AND MEANS RESPONSIVE TO SAID RESISTANCE MEASURING MEANS FOR RECORDING THE RESISTANCE OF SAID DEVICE WHEN THE LATTER IS CONNECTED INTO SAID BRIDGE CIRCUIT.