The error analysis and improvement of microwave resonant cavity method in steam turbine exhaust wetness measurement

This paper analyses the theory of wet measurement using microwave cavity and designs cylindrical resonator sensor with coaxial-cylindrical waveguide circuit grid divider which works with TE₀₁₁ mode and has higher quality factor. Rectangular waveguide is adopted to excite and couple with cylindrical resonator sensor at the end of the waveguide through small hole. The result shows that the resonator humidity sensor meets the practical requirements of humidity measurement system. This paper analyses the uncertainty of the theory formula for measuring the humidity of wet steam on-line. Based on perturbation theory, a formula for engineering is deduced according to the theory that the energy storage of electric field equals the energy storage of magnetic field when resonance is happened. This paper analyses and compares the errors caused by three kind of formula, and the theoretical uncertainty comparison curve is given. The result shows that the measurement accuracy can be increased more than three times with the formula presented in this paper.