Wetness measurement theory based on microwave differential technique

A wet steam humidity measurement method based on microwave differential technique is presented in this paper. The calculation model of equivalent dielectric constant of wet steam at different temperature and pressure is established. The measurement system is designed, which substitutes additional instrument for integrated module and uses two resonators to counteract system error. The principle of system is deduced, and the relationship of variation of steam humidity and output of system is given. System is simulated by use the S parameter of practical resonator. Data show that humidity and system output have high linear relationship. The consistency of theory and simulated data shown the validity of this theory and can be used for the online measurement of flowing wet steam. The accuracy of system in this paper can reach plusmn0.1% near the temperature 30 V.