Guralp Systems CMG-DM24 - Manual (Page 9)

Operator’s Guide DM-24 Digitiser
Issue G January 2003 7
CMG-DM24 FEATURES:
•
built-in Digital Signal Processor (Motorola 56002) provides simultaneous multiple
sample rate data streams at user selectable rates. Up to 4 streams of data for each
component are available at sample rates from 200 samples/second down to 1sps.
•
precision microprocessor controlled time-base synchronises Analogue to Digital
Converters, and DSP and time-stamps data blocks.
•
time synchronisation to external GPS or serial time code.
•
control microprocessor (Hitachi H8) formats and buffers data in on-board 512k RAM
ring buffer.
•
compressed data format (Güralp Compressed Format) for efficient storage and
transmission.
•
serial data output (RS232) at user selectable baud-rates - options of RS422, DPSK or
fibre-optic.
•
built-in microprocessor system configuration and sensor control such as locking,
unlocking, centring and calibration.
•
very low system power consumption, less than 1.5W.
•
Flash EEPROM for program code and filter coefficients.
•
FLASH memory data storage (16 Mb standard) upto 1 Gb options available.
There are six housing configurations in which the CMG-DM24 can be provided. These
are:
a) CMG-DM24 module which plugs straight onto an existing CMG-1T, CMG-3T,
CMG-3ESP or CMG-40T broadband sensor.
b) CMG-DM24 unit in a stand-alone waterproof portable housing with differential high
impedance pre-amplifier unit.
c) CMG-DM24 unit with a differential high input impedance pre-amplifier module
which is housed inside a 19 inch rack with isolated BNC type input plugs.
d) CMG-DM24 unit with very low noise pre-amplifier module to be interfaced to an
electromagnetic seismic sensor.
e) CMG-DM24 unit housed inside the pressure casing of a broadband borehole
seismometer.
f) CMG-DM24 unit housed within the pressure housing of an ocean bottom
seismometer.
All the configurations described above are based on the same CMG-DM24 system
design. Variations between different configurations are due to the application of the
CMG-DM24 digitiser rather than a complete system design change, for example the
surface CMG-DM24 unit. Also, the borehole CMG-DM24 unit is equipped with 16
additional 16-bit slow sampled ADC channels to digitise sensor mass position outputs,
inclinometer and other related analogue signals.
This operator’s guide is applicable to both the CMG-DM24 digitiser module, which fits
onto the top of CMG-broadband sensors and the stand-alone portable CMG-DM24