Memoirs of the Kakioka Magnetic Observatory Vol.08 No.02， p.47, March, 1958
On the Measurement of Earth-Resistivity
The current devices for the apparatus of direct measurement of earth-resistivity are generally based on the Gish-Rooney's apparatus or ratiometer. Longer the base length becomes, the more the signal from the inner electrodes reduces. The double commutator may be a seat of the troublesome instability brought about on the measurement by longer bases, especially for routine use of daily measurements. Mutual inductance between the current-lines and potential-lines effects on the ratio V/I measured by null method. On these standpoints, some modifications including the two phase compensation of ratio meter are taken into consideration and an apparatus for routine use is devised (Fig. 2). Some experimental and field tests are shown.