Patent ID: 6232786
Filing Date: 2001-05-15
Classification: G01N,G01R

Abstract:
A method of compensating for unknown parallel capacitance during measurement of the resistivity of a liquid, comprising the steps of:(1) placing said liquid in communication with a pair of cell electrodes;(2) placing a reference resistance in series with said cell electrodes;(3) connecting a periodic, alternating electrical drive potential across the series combination of said cell electrodes and said reference resistance;(4) measuring a potential difference across said cell electrodes;(5) determining a first crossover time at which said potential difference across said cell electrodes undergoes a first change of sign between a negative and a positive value;(6) determining a second crossover time when said potential difference across said cell electrodes undergoes another change of sign between a negative and a positive value;(7) measuring a potential difference across said reference resistance;(8) generating a reference integrand by integrating said potential difference across said reference resistance for a time period extending from said first crossover time to said second crossover time;(9) generating a cell integrand by integrating said potential difference across said cell for a time period extending from said first crossover time to said second crossover time;(10) calculating a ratio between said cell integrand and said reference integrand; and(11) multiplying said ratio by said reference resistance.