4setting the gain, 1 disassembly – Guralp Systems CMG-5TD User Manual
Page 10
Setting the gain
4
Setting the gain
The built in 5T sensor has a very large dynamic range. In order to exploit the
whole of this range, two separate outputs are available, one with high gain
and one with low gain. Normally, the high gain outputs are set to output a
signal 10 times stronger than that from the low gain outputs. Only one set of
outputs – low gain or high gain – is sent to the digitiser; the selection of which
output to digitise is made using internal jumpers.
Note: To change the gain, it is necessary to open the instrument.
This work must be carried out in a clean environment in order to
prevent contamination of the mechanical components by air-borne
dust.
Caution: The CMG-5TD include components which can be
damaged by electrostatic discharge (ESD). Always work on a
properly grounded dissipative surface and wear a suitable
grounded wristband. Ground yourself by touching an earthed
conductor before handling any of the circuit boards.
4.1
Disassembly
In order to change the gain-setting jumpers, remove the instrument's lid as
follows:
•
Use a large, flat-bladed screwdriver to remove the pressure-release
screw located on the instrument's lid next to the bubble-level.
Warning: GSL instruments are assembled at near to sea level.
When using the instrument at altitude, there may be a
considerable pressure differential between the air inside the
casing and the external atmosphere. This could cause the
screw to fly off with considerable force when initially
released. Take care that this does not cause injury.
•
Use a small, flat-bladed screwdriver to remove the six small screws
located around the edge of the top of the lid.
•
Note the location of the lid with respect to the body. Use a pencil or
adhesive tape to mark both so that the instrument can be reassembled
in the correct orientation.
•
Using a medium, flat-bladed screwdriver, gently prise the lid away
from the body. A slot is provided in the top of the cylinder for this
purpose.
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Issue D - April 2013