The production which optimization and a MEMS technique of the flow direction and velocity sensor

This research is about a thermal flow sensor, suggesting a new structure to improve the detection of airflow directions in any flow direction as well as to realize its interface circuit with simple OP amp circuits. A flow direction sensor was fabricated using MEMS technology. Pt was used as resistive material because of its very stable physical properties. The structure of the sensor, consisting of one heater at the center and four detectors surrounding the heater, is a symmetrical circular-type to generate uniform output regardless of various flow directions. The designed sensor operates based on the relative output difference of the four detectors in response to temperature variations induced by airflow. Therefore, flow directions can be easily detected by amplifying and calculating each output signal of the four detectors. As a result, the interface circuit could be realized with simple circuits. It was designed with popular instrumentation amplifiers and OP amps and integrated into ASIC chips using CMOS technology. The fabricated sensors were tested at 5 m/s and 10 m/s. The response time was some ten seconds and the maximum angle difference compared to flow angle was 5°. The results demonstrate that the suggested structure of sensors could be applied to the detection of flow directions and the test results could be obtained with a simple interface circuit.