Identification of Dynamic Characteristics of TemperatureSensors

When submersible temperature sensors (TSs) are used to measure non-stationary temperatures or applied in systems for automatic control of non-stationary temperatures, it is necessary to know dynamic characteristics of the TSs. In Russian standards, dynamic characteristics of industrial TSs are specified only by the index of thermal inertia. Dynamic characteristics of some types of industrial TSs cannot be described with the required accuracy only by the thermal inertia indicator. Transmissive (transfer) functions of many TSs have an order of magnitude higher than the first and their time constants depend on the conditions of heat exchange with the measured medium. The aim of the work was to improve the accuracy of determination of dynamic characteristics of submergible TS for industrial and aviation purposes. A new method, based on spectral analysis of signal obtained from an experimental transient characteristic of TS, has been developed, in order to improve the accuracy of determination of dynamic characteristics of individual TS instances. This method makes it possible to determine the time constants of transfer functions that have an order higher than the first with high accuracy. To improve the accuracy of finding the dependence of TS nominal dynamic characteristics on the heat exchange conditions, a new method to construct the characteristic curves of thermal inertia has been developed. The technique is based on the use of two-dimensional regression analysis of experimental transient characteristics of individual instances of TSs, recorded at three or more heat transfer coefficients. Besides, a prediction technique was developed for nominal dynamic characteristics of TS for expected operating conditions, based on the use of established characteristic curves of thermal inertia of TS. Mathematical programs and computational procedures were developed to implement the proposed methods and techniques for determination of dynamic characteristics of TSs. The studies have shown that the proposed methods improve the accuracy of determination of dynamic characteristics of both submersible industrial TSs and aircraft gas temperature sensors.