Expanded scale voltmeter bridge circuit having equal value linear and non-linear impedance arms at balance

Claim 1

AN EXPANDED SCALE VOLTMETER CIRCUIT COMPRISING THREE RESISTORS AND A ZENER DIODE COUPLED TOGETHER TO FORM A BRIDGE CIRCUIT HAVING THREE LINEAR BRANCHS AND ONE NONLINEAR BRANCH, SAID BRIDGE CIRCUIT FURTHER INCLUDING A PAIR OF INPUT TERMINALS FOR RECEIVING A VOLTAGE FROM A SOURCE OF VOLTAGE TO BE MEASURED AND ALSO INCLUDING A PAIR OF OUTPUT TERMINALS, A METER CONNECTED BETWEEN SAID PAIR OF OUTPUT TEMRINALS AND HAVING AN INDICATOR WHICH IS AT REST POSITION WHEN SAID BRIDGE IS BALANCED, SAID ZENER DIODE BEING OF THE ALLOYED JUNCTION TYPE, SAID ZENER DIODE FURTHER HAVING A RELATIVELY LOW VALUE OF BACK CURRENT IN THE NONZENER REGION OF ITS CHARACTERISTIC CURVE AND A RELATIVELY SHARP TRANSITION BETWEEN THE NON-ZENER AND ZENER REGIONS OF ITS CHARACTERISTIC CURVE, EACH OF SAID RESISTORS BEING APPROXIMATELY EQUAL TO EACH OTHER IN RESISTANCE VALUE, SAID RESISTORS FURTHER HAVING A RESISTANCE VALUE EQUAL TO THE BACK IMPEDANCE OF SAID ZENER DIODE WHEN SAID METER INDICATOR IS IN SAID REST POSITION, WHEREBY THERE IS PROVIDED AN EXPANDED SCALE VOLTMETER HAVING AN IMPROVEMENT IN SENSITIVITY BY A FACTOR OF APPROXIMATELY 10, AND ALSO HAVING SIGNIFICANTLY REDUCED ERROR DUE TO TEMPERATURE CHANGES.