Feedback Control Theory for Constant-Temperature Hot-Wire Anemometers

Abstract

A feedback control theory for constant‐temperature hot‐wire anemometers is developed in the form of a linear differential equation of the third order. This theory allows a more detailed and clearer description of the anemometer's behavior than can be obtained by the frequency response method which has been applied until now to constant‐temperature hot‐wire anemometers. The theory is presented for the case of an equal arm bridge in the feedback system. Although the theory is restricted to small velocity fluctuations, it is assumed that large fluctuations may be measured correctly within approximately the same frequency range as small ones. The theory is applied to the optimization of the frequency response of constant‐temperature hot‐wire anemometers by means of a square wave test.