Guralp Systems CMG-DM24 - Manual (Page 31)

Operator’s Guide DM-24 Digitiser
Issue G January 2003 29
SENSOR MASS CONTROL
When the digitiser is installed directly to a Guralp seismometer the mass locking and
centring can be controlled if the seismometer supports these operations. The digitiser
needs to be configured for the correct sensor type so that the appropriate commands are
available (see options under the System ID tab).
Four different sensor types are currently supported:-
•
CMG-40T- no mass lock or centring
•
CMG-3ESP- manual mass lock and remote centring
•
CMG-3T- upgraded ‘analogue’ instrument
•
CMG-3TD- fully digital borehole instrument (extra button available when
borehole instrument is switched on)
The three buttons Lock, Unlock, and Centre will lock and unlock the sensor mass for
transportation then re-centre the mass for operation when installed. While they are
executing, the system displays the mass positions for the 3 components, updated once
per second per component (3 seconds to cycle through the 3 components). The mass
positions are measured to 16 bits. When the masses are locked therefore, the displayed
readings will be in the region of 32k or -32k. When the masses are correctly centred the
readings should be less than 1000 counts.