Abstract: A caliper logging sonde is equipped with a plurality of fingers (54) mounted swivelably with respect to its body member (51). The movement of each finger (54) is transmitted to a respective bar (176) in magnetic material. This bar moves within a longitudinal tube (136) which is mounted in a sealed manner with respect to the sonde body member so that its interior is subjected to the pressure outside the sonde and so that the space around this tube is not subjected to this pressure. Around the tube is mounted a transducer winding (150) whose self-inductance depends on the degree of penetration of the bar (176) and hence on the displacement to be measured. A measurement of this self-inductance is obtained by the study of the variation of a current going through the coil when a voltage transient is applied to the coil terminals.

Abstract: This invention relates to equipment which is installed in oil wells and more particularly to a tool control apparatus for a tool placed in the production string of a well.This apparatus is lowered into the well at the end of a cable (116). It comprises a first mechanism (134-148-152-154) for transforming a longitudinal reciprocating movement into an alternating rotary movement, the longitudinal movement being obtained by pulling on the cable (116), and a second mechanism (156) forming part of the first, for transforming the alternating rotary movement into a one-directional rotary movement.The invention also relates to an apparatus for closing the production string of a well, characterized in that it includes the closing apparatus or plug involved.Application to oil well production tests.