A Capacitance 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. A new capacitance humidity sensor is described that has a design, construction, and material composition that impart a unique combination of properties. This humidity sensor also has an ease of fabrication that makes it an improvement over other capacitance-type humidity sensors. The humidity-sensitive film is a multilayered polymeric film consisting of a humidity-sensitive dielectric core, two conductive layers, and two bottom layer strips. The element has a nominal capacitance of 1000 pF and a humidity sensitivity of approximately 4.0 pF/percent RH at 50-percent RH. The characteristics of the humidity sensor, which include the element's sensitivity to relative humidity, response characteristics, and the effects of temperature, are discussed.