Reducing the Effect of Parasitic Capacitance on the Micro-capacitive Humidity Sensor

It is the most important issue of how the effects of parasitic capacitance can be reduced during the development of micro-capacitive humidity sensor systems. For this purposes, in this paper, step-by-step optimizations were carried out through packaging and circuit to achieve a high-precision, high-stability, and high-repetition humidity sensor system. In order to facilitate the designation and optimization, a MEMS humidity capacitive sensor and a discrete capacitance detection PCB circuit were designed. Subsequent theoretical modeling of the capacitance detection loop was adopted for detailed analysis. Finally, the different optimized samples were tested for humidity response; different experimental results were compared and discussed. It is proved that the optimized sensor system reduced the influence of parasitic capacitance on humidity detection effectively, the hysteresis error was reduced from 2% RH to 0.3% RH, the stability and repeatability were greatly enhanced. This also provides a reference for the integrated design of high precision micro-capacitive humidity sensors.