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In-situ calibration of inhomogeneous thermocouples by integrated miniature fixed-point cells; 320–337

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Author

Frank Bernhard

Abstract

According to the gradient theory, the emergence of the thermovoltage takes place only in sections of the thermocouple with temperature gradient. It is shown that, in the case of inhomogeneous thermocouples, the thermovoltage measured does not depend only on the temperatures of hot and cold junctions, but also on the temperature profile alongside the thermocouple. As in the case of an external calibration the temperature profile is never the same as in the real application, any correction of inhomogeneous thermocouples based on it will be imperfect. However, thermocouples with integrated miniature fixed-point cells allow also in case of inhomogenity a correct and automatic in-situ calibration. The paper describes the structure and mode of operation of such thermocouples and reports on the experience of their application in the hot-steam area of power stations.

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