CMG-3V
3 Installing the 3V in a borehole
Before installing any instrument in a borehole, it is recommended that
you prepare the installation site so there is clear access all around the
hole.
•
Keep the borehole capped at all times except when inserting or
removing the instrument, so that debris and tools do not
accidentally fall in.
•
Lay out the cables beside the borehole, or set up a cable drum
nearby, so that they do not become tangled.
•
Ensure the tripod is tall enough to hang the entire installation
(sensor and strain relief unit or digitizer) from it, with the sensor
of the ground.
•
Use a winch with a depth gauge if possible, or measure out the
cable beforehand.
Most installations are equipped with a strain relief unit, which consists
of a metal arm that swings out from the load-bearing cable to wedge
against the side of the borehole. This removes any strain in the load-
bearing cable and prevents vibrations from the surface from being
transmiied t o t he i nstrument. I n i nstallations w ith a d ownhole
digitizer, the strain relief arm is fied to the base of the digitizer sonde;
the phrase “strain relief unit” in the following instructions should be
taken to refer to the digitizer's strain relief arm.
3.1 Installing a sensor with hole lock unit
1. Connect the signal cable to the connector on top of the sensor.
Ensure that the “O”-rings inside the housing are clean, and
tighten the knurled connector nut to its end stop.
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