Transfer function analysis of the constant voltage anemometer

The transfer function for the constant voltage anemometer (CVA) circuit has been derived in terms of circuit and hot-wire parameters and the expressions for the natural frequency and damping ratio have been obtained. Bandwidth in each case was determined from the plot of the normalized transfer function. The theoretical bandwidth behavior calculated from the transfer function plots for the prototype agrees with independent tests of the prototype using laser radiation heating of the hot wire in an air jet. The near constant value of the bandwidth of the CVA with the variation in the hot-wire overheat and its Reynolds number that were observed with the laser tests have been substantiated with the theoretical values from the transfer function. Bandwidth testing with sine wave injection, in situ time constant measurement for proper compensation setting, method to optimize the design to have nearly a constant bandwidth even with different compensation time constants and the operational advantages of CVA are also discussed.