Response compensation of thermistors: Frequency response and identification of thermal time constant

The purpose of this study is to improve the accuracy of general-purpose temperature sensors (commercially available thermistors) in fluctuating temperature measurement and to extend their applicability. First, heat transfer models reflecting the internal structures of plate-type and spherical thermistors were proposed to obtain theoretical frequency response to temperature fluctuations. Second, parameters dominating the response characteristics of the thermistor were extracted, and it was shown that the thermistor response can be approximated by a first-order system. Finally, a flexible response compensation technique for the thermistor was constructed, the development of which has been very difficult because the thermal time constant varies greatly depending on the flow velocity and physical properties of the fluid surrounding the thermistor. The technique utilized a two-thermocouple probe method—rational identification of thermal time constants and digital compensation for response delay—proposed by Tag...