THE PULSE-WIDTH MODULATED-CONSTANT TEMPERATURE ANEMOMETER

A new technique to (i) maintain the resistance of a fine wire probe at an elevated and a 'constant' value, and (ii) utilize the duration of the heating current as a measure of the effective cooling velocity is reported here for the first time. The pulse width modulated (PWM)-cons tant temperature anemometer (CTA) is inherently a digital device given the discrete times at which the output (as a parallel 16-bit number) is presented to the recording device. The advantages of this new devic e over a conventional CTA are noted. The need for additional performan ce measures is also clarified.