Guralp Systems CMG-DCM build <10,000 User Manual
Page 107
Acquisition Modules and Platinum Firmware
Digitiser Configuration
packet and limiting packets to twenty records guarantees reasonably
low latency.
•
Maximum, recommended for 250sps or more (8 bit 250 records,
maximum 1000 samples): - Optimises line utilisation, allowing
maximum compression and minimising the number of packet headers
transmitted.
•
Minimum for lowest latency (32 bit 5 samples): - Disables
compression, forcing samples to be transmitted as 32-bit differences.
Latency is reduced by limiting the number of records to one per packet.
If the system is connected to a digitiser that is using a different combination of
compression control and sample limits, it will appear as an extra item in the
drop-down menu, labelled Custom. For example: Custom (16-bit 40 samples
max) would appear if these settings had been manually configured from the
digitiser's command line.
8.1.1.7 Decimator outputs
The decimator outputs control which digitiser taps have been configured to
output data, both in continuous and triggered states.
On four-channel digitisers, only the columns Z, N, E and X are displayed. On
seven-channel digitisers, Z, N, E and X represent the outputs from SENSOR A
and Z2, N2, E2 and X2 represent the outputs from SENSOR B.
Note: Do not confuse SENSOR A and SENSOR B, which are
analogue inputs to the digitiser, with Port A and Port B, which are
digital inputs to the EAM.
An optional Highpass filter can be applied to eliminate the effect of any DC
offset in the sensor's output. The available corner frequencies, 100, 300 and
1000 seconds, can be selected from the drop-down menu.
The table below the filter configuration shows the currently configured
continuous and triggered outputs with components in columns and taps in
rows. The number of output columns increases when using seven-channel
digitisers.
Extra taps can be added with the
button. The rates available at
each tap are dependant on the rate selected at the previous tap: the base
sampling rate is 2000 samples per second and each tap can be configured to
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Issue E - February 2014