Sercel SN388 Installation Manual - page 16
INTRODUCTION
FIELD ELECTRONICS
0311267
Issue : April 1998
1-10
1.4.1 24-BIT STATION UNIT (SU)
SN 388 advanced technology reduces the complete seismic channel with its 24-bit
stream A/D converter to a plug-in module the size of a matchbox.
The technology allowed the design of an ultra-compact SU which is field
upgradable by plugging in (or out) modules. This versatile SU covers all the various
kinds of seismic acquisitions, at the optimum cost. Within the same casting, by
installing the proper number of seismic channel modules, the user can select the
desirable configuration :
-1-channel SU
-3-channel SU
-6-channel SU
To prevent any incorrect geophone string connection, the spread in operation must
be composed of homogeneous-type SUs.
However, to add flexibility for P-wave acquisition, the three-channel SU can be
used as a one-channel SU.
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No battery pack
The SN 388 does not require any battery pack to be associated with each SU. With
the SN 388's extremely low power consumption (240 mW per channel) the number
of batteries required along a line is minimum.
For portable or heliportable operations the SN 388 station unit comes with an
unprecedented ratio of 650 g per channel.
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Analog-filter-free and ideal seismic response
Taking advantage of the large dynamic range and the very low distortion of the SN
388's 24-bit-stream A/D converter, the seismic channels are free from any analog
filters. With this design, undesirable phase shifts and temperature drifts due to
analog components are suppressed to obtain the ideal seismic response with
either minimum or linear phase shift. As a result, filter settings at the field level are
no longer required, which precludes any unrecoverable error arising from incorrect
settings. (Sophisticated filtering is preferable where it is non-destructive, that is at
the playback or processing stage).
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24-bit built-in test generator
A 24-bit ultra-low distortion built-in test generator is integrated into every SU, in
order to perform a remote check of the complete acquisition performance, at full
specification, from the CCU without any external oscillator.