A circular-type thermal flow direction sensor free from temperature compensation

Abstract This research is about a thermal flow sensor, suggesting a new structure not only to improve the detection of airflow directions in any direction but also realize flow detection without temperature compensation. A flow direction sensor was fabricated using MEMS technology. The structure of the sensor, consisting of one heater and four sensing parts surrounding the heater, is a symmetrical circular-type to obtain uniform output regardless of various flow directions. The designed sensor operates based on the relative output difference of the four sensing parts in response to temperature variation induced by airflow. Even though the temperature of environments varies, the effect to the four sensing parts is equivalent due to its symmetrical structure. Because of its symmetrical structure and operating principle, the temperature variation caused by environments does not affect the conduct of the sensors. As a result, they do not need any temperature compensation for detecting flow direction. The fabricated sensors were tested at 22 and 32 °C. The response time was a few seconds and the maximum angle difference compared to flow angles was 5° for each test. This result demonstrates that the suggested structure of sensors could be applied to the detection of flow directions without any temperature compensation.

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