Performance Improvement of Integrated MEMS Temperature, Humidity, and Air Velocity Sensors for Application in Smart Buildings

Human thermal comfort is highly influenced by environmental parameters such as temperature, relative humidity (RH), and air velocity in addition to personal factors. The available sensors to measure these environmental parameters are stand-alone and can be very bulky and expensive, especially the air velocity sensor. Therefore, it is a challenge to measure human thermal comfort in smart buildings and most of the buildings utilize only temperature sensor to control the indoor climate. This work integrates multienvironmental sensors (temperature, humidity, and air velocity) on a single chip using low-cost CMOS-compatible MEMS technology. The multisensor chip (MSC) is successfully packaged and tested in experimental setups to characterize the temperature, humidity, and air velocity sensors integrated into it. The experimental results indicated that the air velocity sensor consumed low power (0.75 mW) while still achieving a much higher sensitivity of 123.8 mV/(m/s). Besides, the MSC’s RH sensor achieved an average sensitivity of 15.17 fF/%RH and covered the 7% to 82 % RH range, whereas the temperature sensor demonstrated a sensitivity of 25.2 mV/ $^{\circ}$ C during testing, covering a temperature range of 3 $^{\circ}$ C to 53 $^{\circ}$ C. Furthermore, the crosstalk study concluded that because of the low power operation of the air velocity sensor, a very negligible heat is transferred to the substrate. The overall chip temperature increases only by 0.1 $^{\circ}$ C due to the operation of the multisensors. This is quite low compared to the reported MSCs, where the chips’ temperature raised by 2 $^{\circ}$ C to 10 $^{\circ}$ C affecting the performance of the individual sensors located on the same chip. The results suggested that the developed MSC is promising for measuring environmental parameters in smart buildings in the Internet of Things (IoT) era.