Humidity determination by solid state limiting current sensor

The behaviour of a pinhole type sensor for the determination of humidity (1000–28 000 ppm of water vapour, corresponding to about 3.5 to 90 RH% at 25°C) in N 2 and in N 2/O gas mixtures is presented. The operating temperature of the sensor, consisting of a zirconia-based electrochemical cell with a diameter and a thickness of 10 and 5 mm, is 500°C. Imposing a set of potential (from 0 to 1400 mV) to the electrodes, typical polarographic curves were observed; in the presence of two electroactive species two limiting curves were obtained. Water vapour concentration can be obtained with an error not exceeding ±4%.