Determination of Thermal Time Constant of a Pt100 Temperature Sensor in Still Oil Using the Time Derivative Method

Abstract

An alternative method was developed to determine the thermal time constant of a relatively cumbersome temperature sensor in still oil. A relationship between the take-off gradient, initial temperature, thermal time constant, and final steady-state temperature was deduced. An experiment was then performed using a Pt100 temperature sensor to test the veracity of the relationship. The Pt100 temperature sensor was subjected to five different step changes in temperature from an initial temperature of 60 °C. This resulted in five exponential curves with five different take-off gradients. The linearization method was used to determine the thermal time constant as a control experiment. The new method was then applied to the same data set. It agrees very well with the linearization method within the limits of experimental error.