An alpha-alumina moisture sensor for relative and absolute humidity measurement

A novel humidity sensor using an alpha -alumina porous film has been developed for moisture analysis as well as relative humidity measurement. The humidity sensing dielectric used for the sensor mainly consists of a cylindrical-pore-like alpha -alumina film formed by anodic spark deposition, with a dense amorphous alumina thin barrier layer at the pore base formed by reanodization. The performance characteristics of the sensor, e.g., humidity sensitivity, humidity hysteresis, temperature dependence, response time, reproducibility, and long-term calibration stability, were studied in detail. It was found that the sensor can be used for absolute humidity detection in the range from -80 degrees C to -10 degrees C frost point as well as for relative humidity (RH) measurement from 10% to 100% RH with very stable performance.<>