Porosity sensor by using quartz crystals and two excitation signals

In response to a need for a more accurate porosity measuring method for small solid samples (approximately 1 g in mass) the porosity measurement sensor using a sensitive capacitive-dependent crystal was developed. This paper presents the new sensor and the probe sensitivity, frequency dependence on the volume. In addition, the new idea of excitation of the entire sensor with stochastic test signals is described, and the porosity measuring method is provided. The latter includes the influence of test signals on the weighting function uncertainty. The experimental results of the porosity determination in volcanic rock samples are presented. The uncertainty of the porosity measurement is less than 0.1 % in the temperature range 10-30 /spl deg/C.