Guralp Systems CMG-EDU - Manual (Page 7)

Operator's guide
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If the vault is inside a larger structure, its foundations are
separated from the pier, so that nearby vibrations are not
transmitted to the sensor.
A high-quality seismic vault can be incorporated into the construction
plans of a new building at relatively low cost. However, if you are not
in a position to build a dedicated vault, you can still reduce noise to a
satisfactory level by
•
installing below ground, in the basement or sub-basement of an
existing building;
•
placing the sensor directly on a cement floor to improve contact;
and
•
locating the sensor in a quiet corner away from people and
machinery (e.g. air conditioning and heating systems, elevators,
etc.)
Installation on higher floors is not recommended, especially for
horizontal sensors, since any “give” in the floor near the sensor will
cause it to tilt slightly and register a signal.
2.1.2 Temperature stability
The CMG-EDU can operate over a wide temperature range (–10 °C to
+75 °C). However, the sensor mass is sensitive to fluctuations in local
temperature. This affects the response of the instrument at long
periods. Sunlight and other bright lights can also cause small
mechanical stresses that will be detected by the sensor. You can
minimise these effects by
•
installing in a basement, where the temperature is normally
more stable than above ground;
•
locating the sensor in a dark, protected corner, and
•
enclosing it in an insulated box (expanded polystyrene works
very well). This also helps protect the sensor from air currents.
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