Guralp Systems CMG-3TB - Manual (Page 24)

CMG-3TB
unit, there will be an additional dial compared to the unit
pictured; turn this until the built-in ammeter reads around 0.1
A.
2. When the arm makes contact with the borehole casing, the
current will drop slightly. Continue holding the switch in the
EXTEND JAW position.
3. When the lock arm reaches its fully extended position, the
motor will automatically stop and the current will drop to 0 A. If
using a deep-borehole unit, return the dial to zero.
4. If the current has not dropped quite to zero after 30 – 40 s of
operation, release the switch, wait a few seconds, and push it
back to the
EXTEND JAW position briefly. If the arm is not
completely extended, you will see a surge of current. If the
current remains constant, the jaw is at its maximum reach.
5. Once the sensor is locked in place, it is recommended that you
remove the hole lock power cable and control unit from the site.
Without power, the hole lock will not be able to retract, and the
sensor will be secure.
Disengaging the hole lock
To retract the jaw of the hole lock:
1. Tension the load bearing cable, to take up any slack.
2. Hold the switch on the hole lock control unit in the RETRACT
JAW or – position. If using a deep-borehole control unit, also
turn the dial until the built-in ammeter indicates 0.3 – 0.5 A.
More current is drawn retracting the arm, because the motor is
now working against the spring.
3. When the lock arm reaches its fully retracted position, the
motors will automatically stop and the current will drop to 0 A.
If using a deep-borehole unit, return the dial to zero.
Manual operation
If you prefer, you can operate the hole lock by applying voltages
directly to the sensor.
•
To extend the jaw, connect the Hole Lock Motor pin on the
sensor (or on the breakout box's HCU or RECORDER connectors)
to a +12 V power source, and the Hole Lock Motor Return pin to
24 Issue C