One-bodied humidity and temperature sensor having advanced linearity at low and high relative humidity range

Abstract

We present one-bodied humidity and temperature sensor having advanced linearity at low (8–30% RH) and high (90–97% RH) relative humidity range. One-bodied sensor for measuring relative humidity and temperature have been developed using thin-film surface micromachining technology. The sensor have a substrate with a resistor, which is placed between a pair of interdigitated electrodes. The resistor can be used as temperature sensor by measuring resistance variance to temperature change. Humidity can be estimated by measuring capacitance between the resistor and interdigitated electrodes. We present simulation methods used to obtain capacitance and sensitivity as a function of geometric parameters, like the structural width and height, also designed and fabricated a one-bodied humidity and temperature sensor and ASIC. The fabricated sensor showed the linearity (below 2% FS) and low hysteresis (below 2% FS) over a wide range of relative humidity, and the response time of 40 s in adsorption and 70 s in desorption. The sensitivity to temperature of the resistor was about 1 Ω/°C. Our work has demonstrated that one-bodied humidity and temperature sensor can provide an effective means of measuring humidity and temperature of the indoor environment. Experimental results with simulated structure clearly suggest that our fabricated one-bodied humidity and temperature sensor can be used in many applications, such as air conditioning system, feedback controlling in automobile, humidity and temperature chamber, home and hospital, etc.