Being able to rapidly detect a low air flow rate with high accuracy is essential for various applications in the automotive and biomedical industries. We have developed a thermal-based low air flow sensor with a low-power sensor readout for biomedical applications. The thermal-based air flow sensor comprises a heater and three pairs of temperature sensors that sense temperature differences due to laminar air flow. The thermal-based flow sensor was designed and simulated by using laminar flow, heat transfer in solids and fluids physics in COMSOL MultiPhysics software. The proposed sensor can detect air flow as low as 0.0064 m/sec. The readout circuit is based on a current- controlled ring oscillator in which the output frequency of the ring oscillator is proportional to the temperature differences of the sensors. The entire readout circuit was designed and simulated by using a 130-nm standard CMOS process. The sensor circuit features a small area and low-power consumption of about 22.6 µW with an 800 mV power supply. In the simulation, the output frequency of the ring oscillator and the change in thermistor resistance showed a high linearity with an R2 value of 0.9987. The low-power dissipation, high linearity and small dimensions of the proposed flow sensor and circuit make the system highly suitable for biomedical applications.
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机译：对于汽车和生物医学行业中的各种应用，能够快速准确地检测出低空气流量至关重要。我们为生物医学应用开发了基于热的低空气流量传感器，并具有低功率传感器读数。基于热的空气流量传感器包括一个加热器和三对温度传感器，它们可感测由于层流引起的温度差。通过使用层流，COMSOL MultiPhysics软件中的固体和流体物理中的热传递来设计和仿真基于热的流量传感器。建议的传感器可以检测到低至0.0064 m / sec的气流。读出电路基于电流控制的环形振荡器，其中环形振荡器的输出频率与传感器的温度差成正比。整个读出电路是使用130纳米标准CMOS工艺设计和仿真的。该传感器电路具有小面积和800 mV电源的低功耗，约22.6 µW。在仿真中，环形振荡器的输出频率和热敏电阻的变化呈现出高线性，R 2 值为0.9987。拟议的流量传感器和电路的低功耗，高线性度和小尺寸特性使该系统非常适合生物医学应用。
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