Strain gauge compensation

Claim 1

AN IMPROVED STRAIN GAUGE COMPRISING A STRAIN BRIDGE INCLUDING AT LEAST ONE STRAIN-SENSITIVE SEMICONDUCTING ELEMENT AND HAVING OUTPUT TERMINALS AT OPPOSITE ENDS OF ONE BRIDGE DIAGONAL, MEANS CONNECTED ACROSS THE OTHER BRIDGE DIAGONAL FOR THE APPLICATION OF EXCITATION VOLTAGE TO THE BRIDGE, A FIRST TRANSISTOR AMPLIFIER INCLUDING AT LEAST ONE TRANSISTOR HAVING AN INPUT CONNECTED DIRECTLY TO A FIRST OUTPUT TERMINAL OF SAID BRIDGE, A SECOND TRANSISTOR AMPLIFIER INCLUDING AT LEAST ONE TRANSISTOR HAVING AN INPUT CONNECTED DIRECTLY TO A SECOND OUTPUT TERMINAL OF SAID BRIDGE, WHEREBY BOTH SIGNAL AND BIAS VOLTAGES TO THE AMPLIFIERS ARE OBTAINED FROM THE BRIDGE, AND ADDITIONAL RESISTANCE HAVING A NEGATIVE TEMPERATURE COEFFICIENT SELECTED TO ADJUST THE OUTPUT OF BOTH SAID AMPLIFIERS TO COMPENSATE WITHIN SAID AMPLIFIERS FOR VARIATIONS IN SIGNAL AT SAID INPUTS OF SAID TRANSISTORS CAUSED BY CHANGES IN THE TEMPERATURE ENVIRONMENT OF SAID STRAIN-SENSITIVE ELEMENTS, SAID ADDITIONAL RESISTANCE BEING COUPLED BETWEEN THE EMITTERS OF SAID ONE TRANSISTOR OF SAID FIRST AMPLIFIER AND SAID ONE TRANSISTOR OF SAID SECOND AMPLIFIER, AND SAID ADDITIONAL RESISTANCE BEING LOCATED IN PHYSICAL PROXIMITY TO SEMICONDUCTOR ELEMENTS OF SAID BRIDGE THEREBY EXPOSING BOTH SAID BRIDGE ELEMENTS AND SAID ADDITIONAL RESISTANCE TO THE SAME TEMPERATURE ENVIRONMENT, WHEREBY DIFFERENTIAL OUTPUT VOLTAGE APPEARING BETWEEN OUTPUTS OF SAID AMPLIFIERS AS A MEASURE OF STRESS APPLIED TO SEMICONDUCTOR BRIDGE ELEMENTS IS COMPENSATED FOR TEMPERATURE VARIATIONS OF THE BRIDGE.