Guralp Systems CMG-5T - Manual (Page 8)

CMG-5T
1. Prepare a quick-setting cement/sand mixture, and pour it into
the hole.
2. “Puddle” the cement by vibrating it until it is fully liquefied,
allowing its surface to level out.
3. Depending on the temperature and type of cement used, the
mixture will set over the next 2 to 12 hours.
4. Install the sensor as above, cover, and back-fill the emplacement
with soil, sand, or polystyrene beads.
5. Cover the hole with a turf-capped board to exclude wind noise
and provide a stable thermal environment.
If you prefer, you can use quicker-setting plaster or polyester mixtures
to provide a mounting surface. However, you must take care to prevent
the liquid leaking away by “proofing” the hole beforehand. Dental
plaster, or similar mixtures, may need reinforcing with sacking or
muslin.
Installation in Hazardous environments
The fully enclosed aluminium case design of the 5T instrument makes
it suitable for use in hazardous environments where electrical
discharges due to the build up of static charge could lead to the
ignition of flammable gasses. To ensure safe operation in these
conditions, the metal case of the instrument must be electrically
bonded ('earthed') to the structure on which it is mounted, forming a
path to safely discharge static charge.
Where electrical bonding ('earthing') is required during the installation
of a 5T instrument, the central mounting hole that extends through the
instrument should be used as the connection point. This is electrically
connected to all other parts of the sensor case. Connection can be
made by either a cable from a local earthing point terminated in a
8mm ring tag or via the mounting bolt itself.
2.4 Centring the 5T
Once it is installed, you should centre the instrument ready for use.
The offset can be as much as the entire output range of the
accelerometer, which corresponds to around 1 ° from the horizontal or
vertical. You can check that the 5T is within this range by using the
bubble level on the top of the casing: as long as the bubble lies
completely within the scribed ring, the remaining adjustments can be
made internally.
8 Issue E