Impedance Measurement using the Four Electrode Technique

S.E. Locke, T.J. Gale, and D. Kilpatrick (Australia)

Keywords

Biosensors and transducers, impedance measurement,four electrode technique, conductance catheter.

Abstract

This work explores the effect of non-uniform current density between electrodes when measuring impedance using the four electrode (tetrapolar) technique in saline and blood. The analytical solution for the electric potential inside an infinitely long, square cross section isotropic conductor from a point current source and sink in the centre, separated by an arbitrary distance, is presented. Experimentally measured potential differences using the four electrode technique inside long square cross section tubes filled with blood and saline agreed to a few percent of the theory. The work was primarily undertaken to validate experimental technique for use in impedance measurement experiments in sheep. The authors are interested in the use of this method to determine right ventricular volume in the heart.

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