GAS VELOCITY SENSOR

摘要

This invention relates to a gas velocity sensor and to a method of determining gas velocity. The invention provides a method an apparatus for determining gas velocity by generating transmitted radiation having an expected transmission frequency;detecting backscattered radiation; and determining gas velocity in dependence upon any Doppler shift of the frequency of the backscattered radiation; determining a transmission frequency of the transmitted radiation; detecting any difference between the measured transmission frequency and the expected transmission frequency and generating a feedback signal therefrom; determining gas velocity using said feedback signal.