Department of Mechanical Engineering, Chinese Military Academy, Kaohsiung 830, Taiwan; E-Mail:
Sensors (Basel). 2009;9(7):5460-76. doi: 10.3390/s90705460. Epub 2009 Jul 9.
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 ± 7.5° error.
本研究开发了一种基于 MEMS 的低成本传感平台，用于感测气体流量和流向，包括四个以十字形配置排列的氮化硅悬臂梁、悬浮在氮化硅膜上的圆形热线流量计以及集成的电阻温度探测器 (RTD)。在提出的装置中，通过暴露于感测气流的流量计的电阻信号变化来反推流量。为了补偿环境温度对流量测量精度的影响，使用 RTD 产生的电阻信号补偿来自流量计的输出信号。当空气流过十字形悬臂结构的表面时，上游悬臂向下偏转，而下游悬臂向上偏转。悬臂梁的偏转导致其上表面图案化的压阻电阻的电阻信号发生相应变化。每个梁的偏转量取决于流量和梁相对于气流方向的方向。因此，通过对温度校正后的流量进行适当的补偿，可以通过对四个压阻电阻的输出信号进行适当的处理来确定气体流动方向。实验结果证实，集成传感器的输出信号的变化可用于确定环境温度和空气流速，以及相对于传感器的方向，精度为±7.5°误差。
