Analysis of a simple circuit for constant temperature anemometry

Perturbation equations describing the response of hot wires and hot films operating in a simple constant temperature circuit are developed. The heat transfer model shows that at low frequencies (a( omega /K s ) 1 2/ >1) the hot film rolls off at 30 dB/decade. Experimental measurements of the circuit frequency response to a voltage perturbation for both a hot film and a hot wire show good agreement with theory if the calculations use the measured probe time constants, and when thermal end losses are taken into account.