A ceramic humidiy sensor, composed on ZnO, Cr2O3, V2O5 and Li2O, has been developed for use in air conditioners. The ceramic body, which is mainly constructed from ZnCr2O4 spinel grains, is porous. A vanadium compound in the galssy phase is present on the spinel grains and water vapour adsorbs or desorbs on this vanadium compound. The humidity characteristics of the sensor fluctuate gradually and slightly in response to changes in the surrounding atmosphere humidity. However, these fluctuations are less than 7% RH at 25°C after storage under extremely high-humidity conditions (40°C, 90% RH) and low-humidity conditions (40°C, 30% RH).
