In situ calibration of a sensor

摘要

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.