Perfections with skid probes used in geophysics.

摘要

952,813. Borehole logging apparatus. SOC. DE PROSPECTION ELECTRIQUE SCHLUMBERGER. July 20, 1962 [Aug.31, 1961], No. 28027/62. Heading G1N. In a borehole sonde the pressure of the electrodes against the wall of the borehole is made adjustable by a control device located at the surface. A reversible electric motor 23, Fig.1, in the sonde rotates a screw 29 to raise or lower a nut 33, a projection 35 from the nut being located in a groove 37 in the sonde casing. The pressure on electrodes 109, 107 is controlled in accordance with the pressure exerted by a coil spring 47 on collar 53 through a shaft 55 and linkage connected through an equalising collar arrangement in which blocks 75, 76 slide to different extents according to the setting of bar 63 which is dependent on the cross-section of the hole. Links 80, 82, position the wipers of potentiometers 84, 86, to provide bore diameter signals. Information regarding compression of the spring 47 is provided by a potentiometer associated with the projection 35 in the groove 37, the setting of which is a function of electrode pressure and bore diameter. In a modification, the bar 63 is housed in the spring chamber and two rods are brought out through the bottom to blocks 75, 76. A hydraulic arrangement may be used in place of the electric motor, and the output signal may be employed to provide retroactive control application of the invention to sondes carrying different numbers of pads is mentioned and the use of separate motors for each pair of pads is suggested.