Guralp Systems CMG-3ESPC User Manual
Installation
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CMG-3ESPC
Seismometer
Check you have all components and cables:
• CMG-3ESP Compact weak motion broadband
seismometer;
• Thick grey signal cable;
• Sensor calibration data booklet.
You will need a suitable digitizer or recording equipment,
and a 12–24 V DC power supply.
For pit or posthole installations, follow the steps
overleaf.
Choose a suitable site to install the sensor.
The sensor should be mounted:
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4
• at, or ideally below, ground level;
• away from sources of natural noise (e.g. wind, surf);
• away from sources of cultural noise (e.g. traffic);
• in contact with bedrock or, if that is not possible, on a
hard granite or concrete pier;
• in an environment with constant temperature;
• shielded from air currents (e.g. in a polystyrene box)
• away from electrical cables and appliances.
Loosen the brass locking nut on one of the adjustable
feet, then turn the foot, screwing it in or out to level the
sensor. Check using the spirit level on the sensor lid.
Repeat with the other adjustable foot, until the bubble in
the spirit level lies entirely within the inner circle.
Tighten the brass locking nuts downwards to secure the
feet.
If you are using a breakout box, connect the signal cable
between the sensor and the SENSOR connector of the
breakout box, and connect the POWER connector to your
12 V power supply.
Hold down the ENABLE button on the side of the box,
and press the UNLOCK button for a few seconds. The
BUSY LED will light, and you should be able to hear the
internal motors unlocking the masses. CENTRE the
masses if necessary.
See the full manual for detailed usage instructions.
Installing in a pit or posthole
Signal cable
Cover
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Check you have all necessary equipment and select a
suitable location for the pit installation. You will need:
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3
Backfill
Dry sand
Sensor
Marble or
granite plinth
Polystyrene
shielding
• the sensor and other seismic equipment;
• an angle-grinder, if mounting on bedrock;
• otherwise, a supply of dry sand and a marble or
• granite plinth for mounting the sensor;
• a protective shield of polystyrene or other suitable
material.
Dig a pit at least 60 cm deep at your chosen location,
down to the bedrock if possible.
•On bedrock, use the angle-grinder to plane off part of
the surface. Clean the hole and go to step 3 on this
page.
•On compacted subsoil, pour a layer of fine sand over
the bottom of the hole, and mount the sensor on the
granite plinth on top of this sand layer.
In rapid installations, a large stone may serve adequately
instead of the granite plinth.
Connect the sensor cables, then level and unlock the
components as described in steps 3 and 4 overleaf.
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Check the system is working and cover the sensor with its
protective shield.
If you are installing in a cased pit (as in this picture),
install the digitizer and power supply inside if possible,
then seal the installation with a weatherproof cover.
Otherwise, backfill over the shield with fresh soil. Mark
the sensor position, e.g. with its GPS unit. Install the
recording equipment and batteries, if used, in separate
pits.
MSH-C3E-0001-B : Page 2 of 2
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