Measurement and Modelling of the Thermal Response of the Resistance Temperature Sensors

Knowledge of the dynamic properties of thermometers is of particular importance for successful automation of process management in real time. The dynamic behaviour, i.e. the thermal response of the thermometers, is primarily determined by the thermal time constants of the thermo sensor and the protective housing in which it is located (thermo immersion probe, thermowell). In this paper, we presented a simple, but for a large number of applications acceptably accurate method of determining the thermal time constants of the temperature sensor. The procedure for determining the thermal time constants of a thermometer is shown on the example of a thermometer with a resistance temperature sensor. The paper presents the thermal model of the resistance temperature sensor and the protective housing of the sensor. By suddenly immersing the immersion probe in a container with heated water, the temperature response was recorded. Based on the presented thermal model, the thermal time constants of the temperature sensor and the protective case were determined.