Measurement of flow direction and velocity using a micromachined flow sensor

Abstract A circular-type thermal flow sensor was designed and fabricated using MEMS technology in order to detect flow direction and velocity, simultaneously. The designed sensor needs only one heater to operate the flow sensor, so the detection of flow direction and velocity can be accomplished in small dimension and low power consumption. A silicon diaphragm was formed on the back of the sensors to minimize the heat conduction effect and heat capacity. Furthermore, a gap between a heater and four detectors was formed to optimize heat transfer. In order to evaluate the gap effect, a differently structured sensor was designed and fabricated, and their properties were compared. From the tests results of the two designs, the sensitivity of the sensor, which has a gap, is two times more sensitive than the other sensor, which has no gap. Therefore, it can be concluded that the gap between a heater and four detectors is effective for reducing conduction effect. The test results of the designed sensor show the maximum angle difference was 5° and the velocity error was no more than 0.5 m/s. Power consumption was 80 mW and the response time was only a few seconds.

[1]  Miko Elwenspoek,et al.  Thermal flow micro sensors , 1999, CAS '99 Proceedings. 1999 International Semiconductor Conference (Cat. No.99TH8389).

[2]  Isao Shimoyama,et al.  An air flow sensor modeled on wind receptor hairs of insects , 2000, Proceedings IEEE Thirteenth Annual International Conference on Micro Electro Mechanical Systems (Cat. No.00CH36308).

[3]  Sekwang Park,et al.  A circular-type thermal flow direction sensor free from temperature compensation , 2003 .

[4]  Anton F. P. van Putten,et al.  Thermal flow measurements at Gr/Re2≫1 by silicon anemometry , 1999, IEEE Trans. Instrum. Meas..

[5]  Kofi A. A. Makinwa,et al.  A wind-sensor with integrated interface electronics , 2001, ISCAS 2001. The 2001 IEEE International Symposium on Circuits and Systems (Cat. No.01CH37196).

[6]  H. Glosch,et al.  Thermal flow sensor for liquids and gases , 1998, Proceedings MEMS 98. IEEE. Eleventh Annual International Workshop on Micro Electro Mechanical Systems. An Investigation of Micro Structures, Sensors, Actuators, Machines and Systems (Cat. No.98CH36176.

[7]  Frédérick Mailly,et al.  Anemometer with hot platinum thin film , 2001 .

[8]  Jerry S.J Chen,et al.  On the design of a wide range mini-flow paddlewheel flow sensor , 2000 .

[9]  F. Cardarelli.  Materials Handbook — a concise desktop reference: Pub 2000, ISBN 1-85233-168-2. 595 pages, £80 , 2001 .

[10]  A. Michalski,et al.  Flow measurements in open irrigation channels , 2000 .

[11]  Sekwang Park,et al.  A flow direction sensor fabricated using MEMS technology and its simple interface circuit , 2003 .