Wenner procedure

The Wenner method , named after Frank Wenner , is a geoelectrical method for measuring the specific electrical resistances of the subsurface. The resistance of the subsurface is measured with two feeding and two measuring electrodes, the feeding electrodes (A, B) being varied and the position of the measuring electrodes (M, N) being adjusted so that the distances between A, B, M and N are always are the same size.

It is primarily used to determine the change in conductivity over large areas.

1. Measurement principle

4 auxiliary earth electrodes or probes inserted into the earth in a straight line at distance a. A current I is fed to electrodes E and H with a current source G. Then the potential ∆V between the two inner auxiliary earths M and N is measured with a voltmeter.

The value of the resistance R read on the measuring device now enables the calculation of the spec. Earth resistance according to the formula: ${\ displaystyle \ rho _ {w}}$

${\ displaystyle \ rho _ {w} = {\ frac {4 \ cdot \ pi \ cdot a \ cdot R} {1 + {\ frac {2 \ cdot a} {\ sqrt {a ^ {2} +4 \ cdot b ^ {2}}}} - {\ frac {2 \ cdot a} {\ sqrt {(4 \ cdot a) ^ {2} +4 \ cdot b ^ {2}}}}}}}$

With depth b much smaller than the distance a results in:

${\ displaystyle \ rho _ {w} = 2 \ cdot \ pi \ cdot a \ cdot R}$

A related process is the Schlumberger process .

literature

Wenner, F., "A Method of Measuring Earth Resistivity" Report No. 258, Bulletin of Bureau of Standards, Vol. 12, No. 3, October 11, 1915.

Web links

Scan the publication on Archive.org (Engl.)