| 摘要 |
A method in core drilling, wherein a tubular drill bit (8) being arranged at the end of a tubular drill string (6) is driven under rotation against a material intended for drilling, and wherein for the purpose of core retrieving, a tool (17, 20) is brought inside the drill string to an operative position in the area of the drill bit. Acoustic vibrations (24, 25) from the drill string are sensed when the tool is brought to its operative position, sensed acoustic vibrations are analysed for detecting the occurrence of acoustic vibrations characteristic for when the tool has reached its operative position, and an output signal is emitted when the occurrence of vibrations characteristic of when the tool has reached its operative position has been detected. The invention also concerns a device and a drill rig.
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