Guralp Systems CMG-EDU - Manual (Page 39)

Operator's guide
6 Troubleshooting and help
6.1 Troubleshooting
The installation is connected, but Scream! is not receiving any data.
•
Choose File Setup... → from the main menu and open the Com
Ports tab. Check that the baud rate for the serial port attached to
the digitizer is set to 19200, and that all the boxes are checked.
•
Check that the power supply to the sensor and digitizer is
switched on and providing a consistent voltage of 12 – 30 V.
•
Check all connectors and cabling.
The observed signal contains a lot of noise above 1 Hz (1 s).
You are observing “cultural noise” due to human activity. This can be
reduced by choosing a more suitable environment for the sensor.
•
Move the sensor away from noise sources such as machinery
(elevators, air-conditioning units, heating systems, pumps, etc.)
and traffic (pedestrian or motorized.)
•
Mount the sensor below ground level.
•
Enclose the sensor in an insulated box, to reduce the effect of
draughts and temperature fluctuations.
The observed signal contains a lot of noise around 0.2 Hz (5 s).
You are observing natural vibrations in the Earth, known as
microseisms. These are an inescapable fact of life in most locations.
Microseisms can be caused by local storms, rough surf, or large
standing waves in the deep ocean. A large proportion of microseismic
vibrations travel along the surface.
•
To minimise the effect of microseisms, install directly on
bedrock if possible, or underground in a seismic vault.
The observed signal drifts significantly over a long period of time.
This drift is most likely due to temperature fluctuations in the sensor,
caused by changing conditions through the day.
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