Differential structure realization in humidity sensor

To realize the differential structure (which is an effective method to improve the sensitivity) in the humidity sensor, a novel differential humidity sensing structure, which has two kinds of sub units with opposite sensing properties, is designed. The content-based differential humidity sensing device made of conductive polymer composite is used as an example to exhibit the design method. The content-based differential humidity sensing device includes the “negative humidity coefficient unit (NHCU)” and the “positive humidity coefficient unit (PHCU)”. The sensitive material in NHCU/PHCU is the composite with low/high conductive phase content, which results in “a decrease”/“an increase” of the NHCU/PHCU resistance with the increase of the humidity. Through using NHCU and PHCU as the neighboring arms of an electrical bridge, the humidity is converted to a voltage. The results show that the “sensitivity”/“hysteresis error” can be increased/decreased by using the content-based differential structure. The “non-linear error”/“response time” of the content-based differential sensor is between those of NHCU and PHCU.