Frequency response of a 2D flow and thermal property sensor

An enhanced smart flow sensor is being developed at IMTEK in order to measure both flow and thermal properties of fluids at the same time. To be able to measure the thermal properties of a fluid, a sinusoidal voltage is applied at heater. This results in a time-dependent temperature response on a thermistor array. Amplitudes of the temperature signals on the thermistors, and thus the maximum sensitivity range of the sensor depend on the frequency of sinusoidal heating. In this report, we present the frequency response of our thermal flow sensor in nonzero flow conditions. The results are obtained via fluid-thermal coupled simulations. The frequency response shows a common low-pass characteristic of a thermal system. Full temperature amplitude is obtained up to 6 Hz while at 35 Hz 50% of the temperature amplitude remains. This can be used as a design rule for thermal gas flow sensors using a similar topology with a diaphragm.