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A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme
Department of Mechanical Engineering, Chinese Military Academy, Kaohsiung 830, Taiwan
Institute of Precision Engineering, National Chung Hsing University, Taichung 402, Taiwan
Department of Mechanical and Automation Engineering, Da-Yeh University, Changhua 515, Taiwan
Department of Materials Engineering, National Pingtung University of Science and Technology, Pingtung 912, Taiwan
* Author to whom correspondence should be addressed.
Received: 11 May 2009; in revised form: 26 June 2009 / Accepted: 29 June 2009 / Published: 9 July 2009
Abstract: This study develops a MEMS-based low-cost sensing platform for sensing gas flow rate and flow direction comprising four silicon nitride cantilever beams arranged in a cross-form configuration, a circular hot-wire flow meter suspended on a silicon nitride membrane, and an integrated resistive temperature detector (RTD). In the proposed device, the flow rate is inversely derived from the change in the resistance signal of the flow meter when exposed to the sensed air stream. To compensate for the effects of the ambient temperature on the accuracy of the flow rate measurements, the output signal from the flow meter is compensated using the resistance signal generated by the RTD. As air travels over the surface of the cross-form cantilever structure, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The deflection of the cantilever beams causes a corresponding change in the resistive signals of the piezoresistors patterned on their upper surfaces. The amount by which each beam deflects depends on both the flow rate and the orientation of the beam relative to the direction of the gas flow. Thus, following an appropriate compensation by the temperature-corrected flow rate, the gas flow direction can be determined through a suitable manipulation of the output signals of the four piezoresistors. The experimental results have confirmed that the resulting variation in the output signals of the integrated sensors can be used to determine not only the ambient temperature and the velocity of the air flow, but also its direction relative to the sensor with an accuracy of ± 7.5o error.
Keywords: cantilever; flow direction; flow sensor; MEMS; temperature compensation
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Ma, R.-H.; Wang, D.-A.; Hsueh, T.-H.; Lee, C.-Y. A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme. Sensors 2009, 9, 5460-5476.
Ma R-H, Wang D-A, Hsueh T-H, Lee C-Y. A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme. Sensors. 2009; 9(7):5460-5476.
Ma, Rong-Hua; Wang, Dung-An; Hsueh, Tzu-Han; Lee, Chia-Yen. 2009. "A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme." Sensors 9, no. 7: 5460-5476.