Performance of a microwave sensor for the precise measurement of water vapor in gases

A microwave sensor designed for the measurement of humidity in sulfur hexafluoride (SF₆) has been developed for possible in-line use in the electrical utilities industry. This technique could be used to measure efficiently the humidity level to prevent excess moisture and to keep the electrical integrity of sensitive electrical equipment. The measuring system is based on the dielectric properties of the gas mixture at atmospheric pressure and ambient temperature. The voltage difference coming from a measuring cavity resonator and a reference one is related to the amount of water vapor in SF₆. The setup is sensitive enough to detect moisture levels down to 3 ppm