CMOS MEMS Thermal Flow Sensor with Enhanced Sensitivity for Heating, Ventilation, and Air Conditioning Application

In this article, by using 0.35-μm two-polysilicon four-metal CMOS MEMS technology, a thermoresistive micro calorimetric flow (TMCF) sensor with two packaging designs is systematically investigated: Open-space (O-Type) and probe-with-channel (P-Type) designs. In comparison with the O-Type design, the P-Type sensor shows an 80% enhanced sensitivity with a relieved tilt angle effect on the mainstream airflow detection. Accordingly, the P-Type packaged flow sensor for HVAC gains a prominent normalized sensitivity (S∗) of 228 μV/(m/s)/mW, while also having a low power consumption (P) of less than 4.2 mW. Moreover, within the linear range of-2 to 2 m/s, an accuracy of ±0.05 m/s is achieved, thus enabling this robust flow sensor (repeatability <0.2%) for indoor airflow measurements even in a variable ambient environment. Furthermore, the proposed P-Type TMCF sensor and its wireless multisensor module are applied for the development of personalized ventilation and the monitoring of predicted mean vote, both of which confirm the functionality of the developed sensor for indoor airflow measurements in the HVAC system.