Highly sensitive humidity sensor for dielectric measurement (water absorption) in glass-fiber resins

A humidity sensor using a sensitive capacitive-dependent crystal is described. Presented is the probe sensitivity (dependence of df on the dCx). In addition, the idea of excitation of the entire humidity sensor with stochastic test signals is described and the humidity surface-measuring method is given. It includes the influence of test signals on the weighting function uncertainty and on the A/D-D/A conversion. The results of air-humidity measurement and water absorption measurement in glass-fiber resins are shown experimentally. The uncertainty of the surface humidity measurement is less than 0.2% (T=15-25°C and air-humidity=50 to 98%)