Electricity: measuring and testing – Electrolyte properties – Using a conductivity determining device
Patent
1992-07-14
1993-11-09
Wieder, Kenneth A.
Electricity: measuring and testing
Electrolyte properties
Using a conductivity determining device
324439, 204402, 204406, G01N 2706
Patent
active
052606635
ABSTRACT:
Improved circuits for measuring the conductivity of a solution confined between two electrodes in a cell compensate for series capacitance and parallel capacitance between the electrodes. A bipolar square-wave signal is applied to the cell. In one embodiment, the current through the cell is measured by an op-amp in current-to-voltage converter configuration. A feedback resistance employed with the op-amp in a feedback loop is controlled to a low value to ensure that the parallel capacitance is fully charged during an initial portion of each half-cycle of the drive signal. The feedback resistance is then selected so that the gain of the feedback loop is responsive to the range of the resistivity of the solution, and the measurement is made. The period of the bipolar signal is selected responsive to the selected loop gain, to ensure that a filter capacitor across the op-amp is fully charged, and to limit distortion caused by the series capacitance. More particularly, the rate of charge of the series capacitance is proportional to the solution resistance; by varying the period of the drive signal in accordance with the solution resistance, the distortion introduced by the series capacitance remains negligible.
REFERENCES:
patent: 4443763 (1984-04-01), Marsoner
patent: 4496454 (1985-01-01), Berger
patent: 4500840 (1985-02-01), Galwey et al.
patent: 4683435 (1987-07-01), Blades
patent: 4808930 (1989-02-01), Kaiser
Anatel Corporation
Angeli Michael de
Brown Glenn W.
Wieder Kenneth A.
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