Liquid conductivity measurement system using a variable-frequency AC voltage

摘要

A liquid conductivity measurement system is disclosed that accurately measures a liquid's conductivity over a range spanning at least several orders of magnitude using just a single sensor, but minimizing the adverse effects of capacitive and other non-linear factors on the conductivity measurement. The system includes a sensor having two spaced-apart electrodes immersed in the liquid and a drive signal source that applies to the sensor an ac electrical signal having a selected frequency and predetermined magnitude. A voltage detector monitors a sensor voltage signal across the sensor's two electrodes and produces a measurement of the liquid's conductivity. The drive signal source is configured to iteratively adjust the frequency of the ac electrical signal based on the sensor voltage signal, to optimize the liquid's conductivity measurement.