Patent ID: 6496020
Filing Date: 2002-12-17
Classification: G01N,G01R

Abstract:
A method for analyzing a dielectric medium, said method comprising the steps of:measuring, at a test frequency, the capacitance between a pair of electrodes immersed in the dielectric medium, a portion of the capacitance measurement being due to electrode polarization capacitance; and determining either the proportion of said capacitance measurement due to said electrode polarization capacitance or the proportion of said capacitance measurement due to the residual capacitance of the dielectric medium, wherein either of said proportions is determined using a first capacitance measurement made between said electrodes at a first frequency and a second capacitance measurement made between said electrodes at a second frequency, the values of the first and second frequencies being chosen such that the ratio of the respective electrode polarization capacitance values at those frequencies is known, said first and second measurement frequencies lie within a range over which said residual capacitance level is assumed to be substantially constant, said capacitance measurements made at said first and second measurement frequencies are used to calculate the respective electrode polarization capacitances at said first and second measurement frequencies, and the calculated electrode polarization capacitances at said first and second measurement frequencies are substituted in turn into the equation Cpol=Afp (where Cpol is the electrode polarization capacitance at frequency f, and A and p are constants), the resulting equations being solved simultaneously to obtain an expression for estimating electrode polarization capacitance at any frequency.