The frequency response of hot-wire anemometer sensors to heating current fluctuations

Frequency response measurements by the current injection technique of hot-wire anemometers at very low overheat ratios, show that for wires with substantial end conduction losses, a single time constant system response is not obtained. This is contrary to currently used theoretical models. A new model is presented which successfully simulates the measured frequency response characteristics. It is concluded that the traditional assumption of constancy of temperature at the wire ends under dynamic conditions is incorrect. Hot-wires with negligible end conduction losses were found to give the anticipated single time constant system response