A micromachined robust humidity sensor for harsh environment applications

This paper reports a high-sensitive robust humidity sensor using a pair of thermally isolated membranes on which includes meander shaped metal resistive elements are formed. The sensing mechanism of the humidity sensor is based on the difference of thermal conductivity with the amount of moisture in air. The sensor exhibits a sensitivity of 0.054 mV/%RH and a response time of 25 sec. Measurements show a remarkably small nonlinearity of 1% FS and a hysteresis of below 2% over a wide range from 40 to 90% RH. Various reliability tests required for practical use in food processing applications, such as a long-term stability test in high/low temperature (150/spl deg/C/-70/spl deg/C) and high humidity (95% RH) environment and a contamination test, reveal its superior durability in harsh environment.