Measurement of the resistance of an earth-electrode system covering a large area

In an earlier paper the difficulties of measuring the resistance of large electrode systems were discussed, and a method was suggested by which the true value could be obtained. This method was successful but involved the use of very long leads to connect to the potential and current electrodes. An alternative method, in which such long leads are not necessary, has been devised and described. The basic principle is to obtain earth-resistance curves for several current-electrode spacings, and, by assuming a number of successive positions for the electrical centre of the system, to produce intersection curves which will give the earth resistance and the position of the electrical centre. The theory of the method and its application to theoretical cases, a model and a practical case, are described. The conditions to be met in applying this method are also discussed.