A DIGITAL ANEMOMETER

A digital anemometer has been developed for air flow measurements in h ome and office environments. The principle is based on hot-wire anemom etry. The probe consists of a cold thermistor for flow temperature det ection and a hot thermistor for flow rate detection. The latter is sel f-heated by a thermal bridge. Its unbalance voltage due to the air flo w is compared with the reference response transformed into the time do main by direct digital synthesizing. This pulse-width modulation provi des the linear digital representation of the flow rate under measureme nt. The unbalance component due to flow temperature is compensated by scaling the reference response depending on temperature detected by a cold thermistor. These linearization and compensation techniques make accurate measurements possible with a simple configuration. Performanc es of a prototype anemometer built using a one-chip 4-bit microcompute r are also presented to demonstrate the validity of these techniques.