CMG-3V
Surface interface units
In a standard surface control unit, control commands are processed by a
microcontroller within the unit, which then drives motors within the 3V
sensor.
The 3VIC is a variant of the 3V which has an integrated controller
located in its own module within the sensor assembly. Commands are
sent directly to the sensor from a Surface Interface Unit at the pit head.
This system has the advantage that only digital signals are sent to the
sensor, which is particularly useful for deep borehole installations.
(Systems including a downhole digitizer generally do not require a 3VIC
instrument, since the motors can be controlled from the digitizer within
the borehole.)
The Surface Interface Unit is in other respects functionally identical to
the Surface Control Unit supplied with the standard 3V. The rest of this
section applies equally to both types of unit.
Mass locking and unlocking
The 3V is delivered with its sensor mass locked, so that they will not be
damaged in transit. You should lock the mass whenever you need to
move the instrument.
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