The four-point probe technique to measure bio-impedances
Sansen, W.; De Dijcker, F.
Electromyography and Clinical Neurophysiology 16(5): 509-510
1976
ISSN/ISBN: 0301-150X PMID: 1009891 Document Number: 98361
In order to separate the impedance of tissue or bone from the impedance of the tissue-electrode interface a 4-point measurement technique can be used. Four equal electrodes are positioned on 1 row on equal distances from one another. The current from a constant-current source is pushed through the outer electrodes and the potential difference is measured between the inner electrodes. The latter measurement is performed by means of an electrometer such that nearly no current (< 1 pA) flows through the inner electrodes. Hence no oxide is formed and no polarization occurs. This also means that no time variable threshold voltage has to be accounted for in the measurement results.