Abstract: Logging equipment for use in a borehole has a sensor such as an ultrasonic sensor, oriented radially towards the wall of the borehole and rotatable in one direction during measurement about the longitudinal axis of the equipment. In order to allow the sensor to be recalibrated downhole, the equipment also includes a target which is automatically brought face to face with the sensor upon reversal of the direction of rotation of the sensor. The sensor can thus be calibrated under conditions which are as close as possible to the conditions of measurement.

Abstract: An apparatus for guiding flexible sheet material for forming a three-dimensional assembly including a drive device and an edge position detector. The drive device includes a spherical drive wheel moving about two perpendicular axes. A drive roller controls the rotation of the wheel in a vertical plane and a shaft controls its rotation in a horizontal plane. The apparatus provides for measurement of angular position and for control of rotation at the end of the shaft which carries the spindle of the drive wheel. The edge position detector is formed from a strip of photoelectric diodes, a light source, and electronic dircuits providing a control signal for the drive device.