Abstract: An induction log is constructed in a sonde and has at least one or more transmitter coils and at least one or more receiver coils. The sonde supports a power supply and telemetry equipment along with transmitter and receiver apparatus for the coils. The transmitter coils require current levels as much as 1 amperes while the receive signals form output signals which are merely a fraction of a microvolt. The feedpipe array is preferably a feedpipe adapted to be centered in the axial lengthwise portion of the sonde and is further provided with a plurality of openings to enable leads for the coils to be connected. The feedpipe array is formed with a set of multiple steel tubes which are collectively assembled as a bundle on the interior of a copper sleeve.

Abstract: An elongate multilink compound suspension arm is set forth for positioning a sensor parallel to and spaced from a sonde. In particular, it includes first and second approximately parallel arms pivotally connected to a third arm. There are control members additionally included which may be pushed or pulled as appropriate to cause extension arm assembly to move from a fully retracted position in a receptacle along the sonde to an angle extended outwardly and to the rear of the sonde. A sensor pad is supported at the back end and extends toward the back end of the sonde. The sensor pad is pivotally mounted, and is connected with a resilient means for urging the sensor pad into facial contact with the side wall of the borehole. The multilink system particularly enables the sensors on the sensor pad to maintain facial contact with the borehole at a variable distance from the sonde and parallel or at appropriate angles relative to the central axis of the sonde.