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US 4,282,753 AGranted
Combination absolute and differential temperature system
AssigneeThe United States of America as represented by the Secretary of Transportation
InventorWilliam A. Davidson
Life of this patent
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Abstract
The measurement of small differential temperatures over a wide range of absolute temperatures is accomplished by cyclically switching the excitation polarity to a bridge circuit including the temperature sensors. Additionally, the measuring circuitry includes a differential-differential amplifier configuration and a pair of compensating conductors in the cable to each sensor to achieve equal resistance in each excitation path.
Claims10
Apparatus for measuring a temperature differential between two spacially displaced points comprising:
- first temperature sensor means, said first sensor means including a temperature responsive resistance element;
- second temperature sensor means, said second sensor means including a temperature responsive resistance element;
- means for connecting said sensor means resistance elements in adjacent legs of a bridge circuit, said bridge circuit having an excitation terminal;
- a source of excitation current for said bridge circuit, said current source having a pair of opposite polarity terminals;
- means for alternately connecting said bridge circuit excitation terminal to said opposite polarity current source terminals;
- first differential amplifier means connected to first ends of each of said sensor means resistance elements, said first amplifier means providing a signal commensurate with the voltage difference at the said first end of said resistance elements;
- second differential amplifier means connected to second ends of each of said sensor means resistance elements, said second amplifier means providing a signal commensurate with the voltage difference at the said second ends of said resistance elements;
- and
- means connected to said first and second amplifier means and responsive to said signal commensurate with voltage difference for providing an output signal indicative of the difference in the temperatures to which said sensor means are exposed.
6 more elements
Dependencies are inferred from the claim text.