A Resistance Humidity-Sensing Transducer

Recent improvements in the design of humidity-sensing transducers and the materials used in their construction have minimized many of the past limitations of humidity sensors. In this paper a new resistance humidity sensor is described which is an improvement over other resistance-type elements from the standpoint of contamination resistance, stability, and durability. The humidity-sensing element is a multilayered humidity-sensitive polymeric film, consisting of an electrically conductive core and insulating outer layers which are partially hydrolyzed. The element has a nominal resistance of 2500 ¿ and a humidity sensitivity of approximately 2 ¿/ percent relative humidity (RH) at 50 percent RH. The characteristics of the humidity sensor are discussed and include the element´s sensitivity to relative humidity, response characteristics, and long-term stability characteristics. The effects of temperature, air velocity, applied voltage, and type of excitation on element performance are also discussed.