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A Capacitive-Coupled Noncontact Probe for the Measurement of Conductivity of Liquids
Date Issued
01-05-2019
Author(s)
Tejaswini, K. K.
Indian Institute of Technology, Madras
Kumar, V. Jagadeesh
Srinivasan, R.
Sudhakar, Tata
Abstract
A noncontact (capacitive-coupled) probe for the measurement of the conductivity of liquids is presented. Insulation introduced between the measurement electrodes and the liquid intrudes a couple of coupling capacitances. Though the capacitive coupling overcomes the problems of electrode polarization and contamination associated with contacting electrodes, the large reactances of the coupling capacitors pose a problem in the measurement of comparatively very small resistance of the liquid. An auto-balancing signal conditioning scheme presented here overcomes the problem posed by the large capacitive reactances and provides directly a measurable output proportional only to the conductance of the liquid. Error analysis of the probe presented herein helps the optimal design of the probe. A worst case error of ± 0.9% was obtained from a prototype noncontact conductivity probe, developed and tested.
Volume
68