CIRCUIT FOR CONTROLLING THE SIZE OF THE AMPLIFICATION OF SIGNALS PRODUCED BY A TELEVISION TV FOR SOUNDING HOLES AND METHOD FOR IMPROVING THE RESPONSE PROVIDED BY SUCH A TELEVISION

摘要

An electronic circuit is provided for improving the response of a borehole televiewer (10,11) in an out-of-round or off-centre borehole. The circuit comprises an automatic gain control circuit (40,45,47,50,51) having time constants that allow detection of borehole anomalies (50,51) while having a fast enough rise time (45,51) to adjust for the effects of out-of- roundness or the televiewer being off- centre in the borehole. The borehole televiewer comprises a rotating acoustic transducer (10) which is periodically energized to produce acoustic energy that is reflected from the borehole wall back to the transducer. The amplitude of the reflected energy, indicative of fractures, etc., is displayed on a CRT and may be photographed. The CRT sweep is synchronised with a north synchronisation signal produced by a flux gate magnetometer (11) rotating with the acoustic transducer (10). The transducer may be pulsed at a rate of 1500 pps with a rotation period of 0.333 seconds. IMAGE