Determining features in the application of redundancy for the thermistor cubic transformation function using computer simulation

Abstract

The object of research is the process of temperature measurement with a platinum thermistor. We have conducted studies on the cubic transformation function of the thermistor when using redundancy that yielded the equation of redundant measurements of the desired temperature. Owing to this, it became possible to directly apply the resulting equation without additional measures to linearize the function of the thermistor transformation. In addition, the obtained value of the desired temperature does not depend on the values of the parameters of the cubic transformation function and their deviations from the nominal values. Experimental studies have proven that the value of the normalized temperature T0 has a greater influence on the result of redundant measurements and the value of the normalized temperature DT on the entire range of measured temperatures Tx is almost unaffected. The best accuracy results (value of relative error δ=0.02 %) were obtained at T0 values lower than –60 °C. When the error of reproduction of normalized temperatures increased from ±0.02 °C to ±0.1 °C, the best accuracy results (value of relative error δ=0.06 %) were obtained at values of normalized temperature T0 below –130 °C. Analysis of results of the absolute error DT revealed that with an error of reproduction of normalized temperatures of ±0.02 °C and at T0=–180 °C, its value does not exceed 0.02 °C, that is, it is within the error of reproduction of normalized temperatures. This allows us to state that it is recommended to use sources of standardized temperatures of high accuracy during measurement control. Thus, there are reasons to assert the prospect for redundant measurements when directly measuring temperature with a thermistor with a cubic transformation function with high accuracy