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An electrode array is a configuration of
electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
s used for measuring either an
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
or
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
. Some electrode arrays can operate in a bidirectional fashion, in that they can also be used to provide a stimulating pattern of
electric current An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
or
voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to m ...
. Common arrays include: *Schlumberger (Wenner) *Wenner alpha *Wenner beta *Wenner gamma *Pole-pole *Dipole-dipole *Pole-dipole *Equatorial dipole-dipole


Resistivity

Resistivity measurement of bulk materials is a frequent application of electrode arrays. The figure shows a Wenner array, one of the possible ways of achieving this. Injecting the current through electrodes separate from those being used for measurement of potential has the advantage of eliminating any inaccuracies caused by the injecting circuit resistance, particularly the contact resistance between the probe and the surface, which can be high. Assuming the material is homogenous, the resistivity in the Wenner array is given by: :\rho=2 \pi a \frac where a is the distance between probes. Electrode arrays are widely used to measure resistivity in
geophysics Geophysics () is a subject of natural science concerned with the physical processes and physical properties of the Earth and its surrounding space environment, and the use of quantitative methods for their analysis. The term ''geophysics'' som ...
applications. It is also used in the semiconductor industry to measure the bulk resistivity of silicon wafers, which in turn can be taken as a measure of the doping that has been applied to the wafer, before further manufacturing processes are undertaken.Lark-Horovitz & Johnson, p. 54.


See also

*
Four-terminal sensing Four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the si ...
*
Electrical resistivity measurement of concrete Concrete electrical resistivity can be obtained by applying a current into the concrete and measuring the response voltage. There are different methods for measuring concrete resistivity. Laboratory methods Two electrodes Concrete electrical resi ...


References

*Karl Lark-Horovitz, Vivian Annabelle Johnson, ''Methods of experimental physics: Solid state physics'', Academic Press, 1959 . * *John Milsom, ''Field geophysics'', John Wiley and Sons, 2003 . {{electronics-stub Geophysical imaging