NONLINEAR CONTROL THEORY FOR CONSTANT-TEMPERATURE HOT-WIRE ANEMOMETERS

The linear control theory for constant-temperature anemometers can be extended to the nonlinear case which applies for large velocity fluctuations. The nonlinear theory establishes the domain within which the linear theory is valid and reveals some nonlinear effects for large velocity fluctuations. Calculations using a second order approximation have been carried out for velocity fluctuations as large as ±64% of the mean velocity. They show in case of a sinosoidal input function the generation of a second harmonic at the output which limits the usefulness of the anemometer at high frequencies. In case of a large velocity step, a longer time is required to indicate the step correctly than is required for the indication of a small step. © 1969 The American Institute of Physics.