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Operator's guide
digitizer will output data on that channel to the DCM, which will then store or
transmit it with the rest of the data, according to the way it is configured.
Since it is an optional feature, the digitizer may not use the Pressure Mux
channel to report pressure data. If this is the case, that channel may be used for
another purpose. Likewise, the three channels marked Spare may not be used,
depending on the optional features present in the instrument.
For more information on the format of data packets transmitted on the Mux
channels, please refer to the documentation supplied with your digitizer.
Sensor mass control
There are three commands which can be relayed to an instrument through the
DCM to control the position of its sensor mass. For each instrument the buttons
which perform these commands (Centre instrument, Lock instrument, and
Unlock instrument) can be found at the bottom of the relevant Digitizer Setup
page. The type of sensor you have installed determines which, if any, of these
commands have any effect.
• The CMG-40T sensor type has no mass lock or centring capabilities, so
all three buttons are inactive.
• The CMG-3ESP sensor type has manual mass lock and remote centring,
so only the Centre instrument button is active.
• The CMG-3T sensor type is an automated analogue instrument, with all
three commands available.
• The CMG-3TD sensor type is a fully digital borehole instrument, with
all three commands available.
Lock and Unlock instrument are provided so that you can secure the
seismometer's sensor mass for safe transportation. Once installed and unlocked,
you should Centre instrument to move the mass to the correct position to start
measuring data. During the execution of any of these commands, the system
will display the three components of the mass's current position and update
them once per second per component. When the masses are locked, the position
readings will be in the region of 32,000 or 32,000 counts. When the masses−
are correctly centered all three readings should be less than ±1,000 counts.
Locking or unlocking the sensor mass typically takes several minutes to
complete.
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