Measurement of liquid permittivity using one measurement cell

A permittivity sensor using a sensitive capacitive-dependent crystal is described. The probe sensitivity (dependence of df on permittivity) is studied. In addition, a new idea of excitation of the entire sensor with stochastic test signals is described, and a permittivity surface-measuring method is discussed. The latter includes the influence of test signals on the weighting function uncertainty. The results of the permittivity measurement are shown experimentally. The uncertainty of the surface permittivity measurement is less than 0.01% (T=10-30/spl deg/C).