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Inventi Impact - Sensing & Actuation

Articles

  • Inventi:esa/83/14
    A SELF-OSCILLATING SYSTEM TO MEASURE THE CONDUCTIVITY AND THE PERMITTIVITY OF LIQUIDS WITHIN A SINGLE TRIANGULAR SIGNAL
    Sylvain Druart, Denis Flandre, Laurent A Francis

    We present a methodology and a circuit to extract liquid resistance and capacitance simultaneously from the same output signal using interdigitated sensing electrodes. The principle consists in the generation of a current square wave and its application to the sensor to create a triangular output voltage which contains both the conductivity and permittivity parameters in a single periodic segment. This concept extends the Triangular Waveform Voltage (TWV) signal generation technique and is implemented by a system which consists in a closed-loop current-controlled oscillator and only requires DC power to operate. The system interface is portable and only a small number of electrical components are used to generate the expected signal. Conductivities of saline NaCl and KCl solutions, being first calibrated by commercial equipment, are characterized by a system prototype. The results show excellent linearity and prove the repeatability of the measurements. Experiments on water-glycerol mixtures validate the proposed sensing approach to measure the permittivity and the conductivity simultaneously. We discussed and identified the sources of measurement errors as circuit parasitic capacitances, switching clock feedthrough, charge injection, bandwidth, and control-current quality.

    How to Cite this Article
    CC Compliant Citation: Sylvain Druart, Denis Flandre, and Laurent A. Francis, “A Self-Oscillating System to Measure the Conductivity and the Permittivity of Liquids within a Single Triangular Signal,” Journal of Sensors, vol. 2014, Article ID 389764, 11 pages, 2014. doi:10.1155/2014/389764. Copyright © 2014 Sylvain Druart et al. This article is distributed under the Creative Commons Attribution License(http://creativecommons.org/licenses/by/3.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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