# Electrode array

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thumb|250px|The '''Wenner electrode array''' consists of a line of four equally spaced electrodes. Current is injected through the outer electrodes and potential is measured between the inner electrodes.
An '''electrode array''' is a configuration of [electrode](/source/electrode)s used for measuring either an [electric current](/source/electric_current) or [voltage](/source/voltage). Some electrode arrays can operate in a bidirectional fashion, in that they can also be used to provide a stimulating pattern of [electric current](/source/electric_current) or [voltage](/source/voltage).

Common arrays include:
* Schlumberger (Wenner)
* Wenner alpha
* Wenner beta
* Wenner gamma
* Pole-pole
* Dipole-dipole
* Pole-dipole
* Equatorial dipole-dipole

==Resistivity==
[Resistivity](/source/Electrical_resistivity_and_conductivity) 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.<ref name="Milsom_2003"/> 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:

:<math>\rho=2 \pi a \frac {V}{I} </math>

where <math>a</math> is the distance between probes.

Electrode arrays are widely used to measure resistivity in [geophysics](/source/geophysics) applications.<ref name="Milsom_2003"/> 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](/source/doping_(semiconductor)) that has been applied to the wafer, before further manufacturing processes are undertaken.<ref name="Lark-Horovitz_1959"/>

==See also==
* [Four-terminal sensing](/source/Four-terminal_sensing)
* [Multielectrode array](/source/Multielectrode_array)
* [Electrical resistivity measurement of concrete](/source/Electrical_resistivity_measurement_of_concrete)

==References==
<references>

<ref name="Lark-Horovitz_1959">{{cite book |author-first1=Karl |author-last1=Lark-Horovitz |author-first2=Vivian Annabelle |author-last2=Johnson |author-link2=Vivian Annabelle Johnson |title=Methods of experimental physics: Solid state physics |publisher=[Academic Press](/source/Academic_Press) |date=1959 |isbn=0-12-475946-7 |pages=54}}</ref>
<ref name="Milsom_2003">{{cite book |author-first=John |author-last=Milsom |title=Field geophysics |publisher=[John Wiley and Sons](/source/John_Wiley_and_Sons) |date=2003 |isbn=0-470-84347-0 |pages=98–99}}</ref>

</references>

==Further reading==
* {{cite book |author-last=Loke |author-first=Meng Heng |title=Tutorial: 2-D and 3-D electrical imaging surveys |format=PDF |orig-date=1996 |date=2004-07-26 |publisher= |publication-place= |url=http://www.geoelectrical.com/coursenotes.zip |access-date=2007-06-11 |url-status=dead |archive-url=https://web.archive.org/web/20070927184548/http://www.geoelectrical.com/coursenotes.zip |archive-date=2007-09-27}}

{{electronics-stub}}

Category:Geophysical imaging

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Adapted from the Wikipedia article [Electrode array](https://en.wikipedia.org/wiki/Electrode_array) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Electrode_array?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.