On the Equilibrium of Heterogeneous Substances: Difference between revisions

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[[File:Wenner electrode array.svg|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.]]
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An '''electrode array''' is a configuration of [[electrode]]s used for measuring either an [[electric current]] or [[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]] or [[voltage]].
 
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.<ref>Milsom, pp. 98–99.</ref>  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 is given by,
 
:<math>\rho=2 \pi a \frac {V}{I} </math>
 
Electrode arrays are widely used to measure resistivity in [[geophysics]] applications.<ref>Milsom, p. 98.</ref>  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 (semiconductor)|doping]] that has been applied to the wafer, before further manufacturing processes are undertaken.<ref>Lark-Horovitz & Johnson, p. 54.</ref>
 
==See also==
*[[Four-terminal sensing]]
*[[Multielectrode array]]
*[[Electrical resistivity measurement of concrete]]
 
==References==
{{reflist}}
*Karl Lark-Horovitz, Vivian Annabelle Johnson, ''Methods of experimental physics: Solid state physics'', Academic Press, 1959 ISBN 0-12-475946-7.
*{{cite book |last=Loke |first=M.H. |title=Tutorial: 2-D and 3-D electrical imaging surveys |year=2004 |url=http://www.geoelectrical.com/coursenotes.zip |format=PDF |accessdate=2007-06-11 }}
*John Milsom, ''Field geophysics'', John Wiley and Sons, 2003 ISBN 0-470-84347-0.
 
 
 
{{electronics-stub}}
 
[[Category:Geophysical imaging]]

Latest revision as of 23:28, 21 July 2014

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