Analysis of temperature compensating circuits for hot-wires and hot-films

A scheme utilizing a temperature probe immersed in the working fluid to compensate for the dependence of hot-wire (or hot-film) velocity calibration on ambient temperature variations is analyzed. To achieve compensation, only properties of the anemometer bridge, the velocity and temperature probes need to be known. The scheme provides means for incorporating the temperature compensation a priori to conducting the experiments, without the need for temperature calibration. Experiments were conducted, using tungsten hot-wires in air, to check the performance of the analysis and to verify some of the assumptions that were made. For typical probes, with an ambient temperature increase of 20 C, maximum error in the indicated velocity of 1% or less can be achieved.