Design and fabrication of a flow sensor detecting flow direction and velocity

A thermal flow sensor detecting flow direction and velocity at the same time is designed and fabricated using MEMS technology. Pt was used as resistive material because of its very stable physical properties. Only one heater at the center and four detectors surrounding it is necessary to work the flow sensor. Therefore, a flow sensor detecting flow direction and velocity was accomplished in a small dimension. An interface circuit was designed with popular instrumentation amplifiers, Wheatstone-bridge circuit and OP amps, and they are integrated into ASIC chips using CMOS technology. The maximum angle difference was 5/spl deg/ and velocity error was no more than 0.5 m/s. Power consumption was 50 mW and response time was a few seconds.