Observations on the velocity scaling of thermistor dynamic response functions

Abstract

The dynamic response of thermistor temperature sensors is known to be sensitive to the relative velocity between the sensor and the surrounding fluid on both theoretical and experimental grounds. The majority of the experimental investigations derive empirical velocity scaling relationships which have little basis in theory. We have determined that the dynamic response of a particular fast response thermistor scales with the square root of velocity, in accordance with the predictions of the boundary layer theory, over a speed range of 0.5–2 m/s with water as the working fluid.