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Subject: search.filters.subject.Thermocouples

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    Thermocouple signal conditioning using augmented device tables and table look-up neural networks, with validation in J-Thermocouples
    (IEEE, 2022-01-25) Maseko, Moses L.; Agee, John T.; Davidson, Innocent
    The relatively high accuracy, large measurement range, and durability of thermocouple devices make these devices to probably be the most-widely used temperature measuring devices in industrial applications. The ability of thermocouples to sense temperature is derived from the generation of thermoelectric voltages arising due to temperature differences between the hot and cold junctions of the thermocouple. Thermocouple temperature measurement processes suffer from inaccuracies arising from both the unwanted or undetected variations in the cold junction temperature of the thermocouple, and nonlinearities in the generated thermoelectric voltage. This paper presents an enhancement of thermocouple temperature measurement using a combination of augmented thermocouple tables generated from thermocouple polynomial functions, look-up MLP neural networks trained to accept the thermocouple output voltage, and the cold or reference junction temperature measurements: to produce improved hot-junction temperature outputs. Experimental validation of the current approach for a J thermocouple, using data from augmented device tables, reproduced the measured temperature values with a worst-case error of 0.0094%.
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    Preaging techniques as a means of stabilising thermoelectric drift in nickel-chromium/nickel-aluminium thermocouples for use in an aluminium heat treating furnace
    (1991) Hart, Roderick William Wenham; Smuts, D. J.
    This dissertation is primarily concerned with investigating and improving the degree of accuracy and precision that may be achieved from temperat~re measurements made utilising nickel-chromium/nickel-aluminium (Type K) thermocouples. The practice of heat treating extruded aluminium section creates specific metallurgical properties within section. Development of specialised aluminium alloys has necessitated the use of treatment temperatures,- close to the limit beyond which the alloy experiences undesirable, permanent, metallurgical change. This situation has demanded urgent attention to, in quality assurance terms, the, 'fitness for purpose', of primary temperature sensors. The most established of these sensors, the Type thermocouple, has known problems relating to calibration stability and drift. The substantial amount of furnace control instrumentation and cabling dedicated to measurement from Type K sensors precludes the simple conversion to an alternate sensor type. The more practical option of applying calibration correction factors to existing measuring systems is only feasible if sensor stability characteristics permit measurement traceability to' be established within required uncertainty limits.