NEW TYPES OF WELL RESISTIVITY-METERS 393 



The constancy of the coefficient and the small influence of the external 

 medium on these devices are due to the mutual positions of the electrodes A 

 and M (the electrode M is sitviated on the body of the current electrode) 

 and especially due to the shape of the electrode N. Consequent upon the 

 shape of the electrode N the electric field inside the sphere (outlined by the 

 electrode loops) is stable and is not influenced much by changes in resistance 

 and rearrangements in the electric field outside the sphere. It may appear 

 that the electrodes A and M could be placed at the same point. In such 

 a case, however, the measured potential difference would include the poten- 

 tial drop produced by the contact resistance of the electrode A. This would 

 lead to a large error in the determination of the specific resistance, affecting 

 the constancy of the resistivity-meter coefficient. Thus, in designing a resis- 

 tivity-meter one should start from a sonde corresponding to the electrode 

 devices 7 and 8. 



THE DESIGN OF THE RESISTIVITY -METERS 



The well resistivity -meters REU-57 and RSE-3-57* were designed and 

 manufactured on the basis of the most suitable electrode devices. The 

 general shape of the resistivity-meter REU-57 is shown in Fig. 5. 



The principal part of this resistivity -meter, which is open, is an electrode 

 device built analogously to the electrode arrangement 8. 



The body of the resistivity -meter consists of an upper (5) and a lower (3) 

 parts connected by three tension shackles {4). The electrode device (i) 

 is tightened in a holder (2) -which is welded to the middle of two tension 

 shackles (9) with circular cross-sections. In the upper part of the resistivity 

 meter there is a plug bridge (7) protected by a cylinder (6) and a hood (S). 



The general shape of the resistivity-meter RSE-3-57 adopted for the 

 bore-hole gear OKS is shown in Fig. 6. 



The resistivity -meter consists of an upper (4) and a lower (5) cap a cont- 

 ainer mth large (75°) longitudinal windows, and a brass tube (i) passing 

 through the centre. 



The brass tube with the exception of its middle parts is insulated and 

 protected from the body by a rubber insulator (3), while its bare part serves 

 as the electrode A. Along a spiral groove of the middle part of the tube lies 

 a live wire (5) which is insulated from the tube and serves as a measuring 

 electrode M. The enclosure of the resistivity-meter serves as the electrode A^. 



To avoid the influence of the terminal parts of the resistivity-meter on 



* The construction of the resistivity -meters has been carried out by Ya. A. Magnoush- 

 evskaya and L. O. Globus. 



