ELECTRICAL IMPEDANCE MEASUREMENT USING PULSE EXCITATION

Abraham Mejía-Aguilar, Ramon Pallàs-Areny

Abstract

Impedance is the only electrical property common to all materials. Its measurement is used for material characterization and testing, and for sensor design. Impedance measurements in a broad frequency range are slow and need complex instrumentation. Impedance measurements in the time domain can be faster but need more computation power. We propose a novel measurement method intended for applications where the unknown impedance can be modeled by three independent components. The method consists of applying a single pulse, measuring three amplitudes, and calculating the unknown components from the analytical solution of the resulting equation system. The three measurement points are so selected that the computation power needed is minimal. Furthermore, measurements at the leading edge of the pulse are avoided by using linear extrapolation. The method suits lowpower measurements in electrolytes, which involve electrodes that can be modeled by a resistance shunted by a capacitance. Actual conductivity measurements from 100 μS/cm to 10 mS/cm, yield relative errors below 3.5 %, which fulfills the 5 % target set in some standards for monitoring the conductivity of surface water bodies.

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IMEKO-TC4-2008-135.pdf

DOI

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IMEKO TC

TC4 - Measurement of Electrical Quantities

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