Automatic thermocouple reference junction compensator
AssigneeThe Boeing Company
InventorsEugene T. Ihlenfeldt, David E. Marshall
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Abstract
A system for automatic cold-junction referencing of thermocouples in temperature controllers wherein a differential amplifier is used to amplify the thermocouple signal prior to establishing the cold-junction compensation and measuring range. This permits the use of command signals from any floating or single-ended source, making the controller compatible with existing traditional command generators and with computer systems with digital-to-analog converters. The amplifier isolates the thermocouple from the remainder of the circuitry such that it can be grounded on the heated part.
Claims4
Temperature measuring apparatus comprising a measuring thermocouple adapted to be placed in contact with an object whose temperature is to be measured, thermocouple reference junction means connected in series-opposition with said measuring thermocouple, [a] temperature compensation [resistor] means whose [resistivity] output signal varies as a function of ambient temperature, first and second differential amplifiers each having a pair of input terminals, ungrounded conductors connecting said measuring thermocouple and said reference junction means across the input terminals of said first differential amplifier, a source of bias voltage, and means [connecting said source of] for applying said bias voltage, the output signal of said first differential amplifier, said output signal of said compensation [resistor] means and a temperature command signal to one of the input terminals of said second differential amplifier, the other input terminal of said second differential amplifier[, said source of bias voltage and said compensation resistor] being connected to ground.
Dependencies are inferred from the claim text.