Guralp Systems CMG-3T - Manual (Page 9)

Operator's guide
board ADCs.
Breakout box and hand-held control unit
The 3T can be supplied with an optional robust breakout box, which
provides mass control functions in installations which do not use
compatible digitizers. A hand-held control unit is also available which
can control calibration lines and monitor sensor outputs in addition to
mass control. See chapter 4, page 30, for more details.
Power supply
The sensor requires a 12 Volt power supply, connected via the socket
and breakout box or digitizer. You will need to make up a suitable
cable to connect a 12 V power source to the 10-pin connector on the
breakout box (spare 10-pin mil-spec connectors are provided for this
purpose.) Using a 12 Volt, 25 Ampere-hour, sealed, heavy-duty, lead-
acid battery, you should expect the instrument to operate for around a
week without recharging.
If you prefer, you can power the 3T directly from the connector on the
top panel (see Chapter 6, page 47.)
A power management module can be installed as an option, which
allows the 3T to operate from a 10 – 15 V supply range. This module
also cuts the input power to the sensor electronics if it drops below
10.5 V, to minimize discharge from battery-operated installations.
Units with serial numbers beginning T33 are provided with a wide
input range DC-DC converter, and can be powered from a 10 – 36 V
supply.
The 3T draws a nominal current of 75 milliamps from a 12 Volt supply
when in use. During locking and unlocking of the sensor masses, this
current rises briefly to 600 milliamps. It is recommended that you
carry a spare 12 Volt battery when visiting an installation for
maintenance, in case the sensor needs to be moved and the on-site
batteries no longer have sufficient charge to perform the locking
procedure.
Signal output
The sensors output voltages representing ground velocity on floating
differential lines. The breakout box provides a RECORDER connector
for attaching to a recording system or digitizer. You can use any multi-
channel recording system, provided that it has high-impedance
floating differential inputs.
If you are using a Güralp Systems digitizer, you can connect the
instrument directly to the digitizer without using the breakout box;
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