Dependence of apparent resistance of four-electrode probes on insertion depth

Jang Zern Tsai, Hong Cao, Supan Tungjitkusolmun, Eung Je Woo, Vicken R. Vorperian, John G. Webster

Research output: Contribution to journalArticlepeer-review

48 Scopus citations


The apparent resistance of a finite-thickness layer measured with a four-electrode plunge probe depends on the electrode insertion depth, electrode spacing, and layer thickness, as well as the resistivity ratio of an underlying layer. A physical model consisting of air, a saline solution layer, and an agar layer simulates the real situation of resistivity measurement. The saline layer represents the finite-thickness layer whose resistivity is to be measured by a plunge electrode probe, and the agar layer represents an underlying perturbing layer. A micropositioner controls the insertion depth of the four electrodes into the saline solution. With the apparent resistance measured on a semi-infinite-thickness layer of saline solution as standard, measurement results show decreasing apparent resistance and increasing error with increasing electrode insertion depth. This information is important for correct measurement of myocardial resistivity in vivo and in vitro.

Original languageEnglish
Pages (from-to)41-48
Number of pages8
JournalIEEE Transactions on Biomedical Engineering
Issue number1
StatePublished - 2000


  • Apparent resistance
  • Electrode spacing
  • Four-terminal impedance measurement
  • In-chamber blood
  • Insertion depth
  • Multiple-layer model
  • Myocardial resistivity
  • Myocardial thickness
  • Plunge probe
  • Probe constant
  • Resistivity ratio
  • Saline calibration


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