Chapter 3. Digitiser Configuration

The DM24 digitiser can most easily be configured using an EAM. Please see the Platinum manual, MAN-EAM-0003, for details. If the digitiser must be configured from its command line, please follow the instructions below.

Bring up terminal mode on the digitiser. This can either be done with Scream or with a terminal emulator such as minicom or PuTTY. You should be presented with a message similar to the following. Hitting a couple of times will ensure the session is responsive.

LW A80800 CMG-3T Command Mode

0 blocks in buffer | 256 blocks free

Guralp Systems Ltd - DM+FW v.103 mgs 17/10/07 (Build 60)

ok_A808

3.1 Update firmware and upload infoblocks

Ensure that the firmware on the DM24 is up to date. At the time of writing, the latest versions are Bootloader 3002, DSP 1091 and system 1.07b26. Later versions will be backwards compatible. Firmware upgrade instructions are online at www.guralp.com/sw/firmware-for-the-cmg-dm24-mk3.

Also upload an info block (or two blocks if you have a two-instrument digitiser). Instructions are at www.guralp.com/howtos/information-blocks-from-guralp-digitisers.

3.2 System identity

Now, set the system identity. This gives the System and Stream IDs of the generated GCF data.

resetlabels ok_A808

set-id

System Identifier { LW } ? 5 characters : LW

Serial # { A80800 } ? 6 characters : A808

LW A80800 CMG-3T ok_A808

If you have a DM24S6, you should enable a second serial number for the second instrument. This is required otherwise the second info block will not be emitted by the digitiser. This is achieved with the serial2 command.

serial2

Secondary Serial # { 0 } ? 6 characters : B808 B80800 ok_A808

GSL recommend that the system identifier is set to the digitiser serial number, and that the stream identifier is set to the last four digits of the sensor serial number.

3.3 Basic setup

These steps should be followed to ensure the digitiser behaves as expected.

6 sensor-type

Sensor type set to CMG-5TD ok_A808

adaptive

Adaptive Storage : Circular ok_A808

erasefile

Are you SURE you want to delete ALL Flash Data? Y/Ny

Erasing ALL 65.5MB

\ 49.1MB

64MB Flash Memory Buffer : 0 Blocks Written 0 Unread 65,536 Free

Oldest data [16] Blank

Read point [16] Blank

Latest data [16] Blank

File Replay [16] Blank ok_A808

normal compression Optimum Compression ok_A808

0 1 bandpass 10.0->90.0HzBandPass ok_A808

3 highpass

HighPass at 1000 sec ok_A808

6 sensor-type tells the digitiser that it is connected to a 5T. This does not alter data acquisition, or the behaviour of the system, but merely disables some commands, such as mass lock/unlock, which are not used with strong motion instruments. The sensor-type command applies only to Sensor A. Use the command explain sensor-type to get a list of additional sensors.

adaptive turns on adaptive mode, in which the digitiser's internal flash is used as a temporary buffer should data not be acquired by a connected system. Other digitiser modes such as FIFO or Direct are also compatible. Consult the DM24 manual to determine which mode is the most appropriate for you. When switching into this mode, the command erasefile is used to clean the flash memory, which may contain stale data.

The compression and bandpass commands are required for correct operation of low-latency mode. The highpass command introduces a highpass filter at 1000 seconds, which has the effect of removing DC offset from the sensor's output. This should improve the quality of the strong motion results.

3.4 Enable strong motion mode

The CMG-DM24 has a flexible system of output taps which can be used to choose which sample rates are transmitted. Strong motion mode requires the first tap be set to 200 samples per second. The configuration below transmits 100sps continuous data, which you can alter as you please. It also transmits the 20sps low-latency data, which are filtered differently (see the section below on low latency data). The low-latency data are always transmitted at 20sps.

The output taps must be configured as follows for correct operation:

200 100 20 10 samples/sec

200 100 20 10 samples/sec ok_A808

The steps below enable low-latency mode, and turn on the 20sps low latency data. Change $77 triggers to simply 7 triggers for a single-instrument system (DM24S3).

lowlatency

Tap0 200 s/s Low Latency mode ( 20s/s ) ok_A808

$77 triggers

Tap0 200 s/s Low Latency mode ( 20s/s ) ZC NC EC ZC NC EC ok_A808

LLstreams enable

Low Latency Data Streams enabled ok_A808

Transmission of the low latency 20sps streams is controlled by the LLstreams command. Since v.103 build 70, low latency is disabled by default and must be explicity enabled with the above command. It can be disabled again with LLstreams disable, if required.

Next, the continuous data transmission should be configured. The first hex code below tells the DM24 to output continuous data from the second tap on both instruments. For a one-instrument digitiser setup, this should be changed to 00070000. The second hex code turns off the multiplexor channels, which are not used for strong motion instruments.

set-config

Hex code to select taps {00770000} 00770000

Hex code to select mux channels {0000} 0000

Tap0 200 s/s

Tap1 100 s/s Continuous: Z2 N2 E2 Z2 N2 E2

Tap2 20 s/s

Tap3 10 s/s ok_A808

The first hex code could be 77000000 to enable 200 sps data on both sensors (or 07000000 for Sensor A only), 00000077 to enable only 10 sps data, or a combination of any of these codes. The DM24 manual can be consulted for further information.

Finally, enable the remaining strong motion features:

+simode ok_A808

rtstatus enable SQpatch disabled ok_A808

ok-1

Forth Vocabulary now available

Guralp Systems Ltd - DM+FW v.103 mgs 17/10/07 (Build 60)

SYSTEM FORTH ROOT

Current: FORTH

ok_A808

+monitor ok_A808

uspmonitor ok_A808

3.5 Common scenarios

This section holds concise instructions for setting up three common scenarios. Ensure that you have read the previous sections and understand what each command does before issuing these instructions.

3.5.1 A single strong motion sensor

resetlabels
set-id
6 sensor-type (for CMG-5T)
erasefile
normal compression
0 1 bandpass
3 highpass
200 100 20 10 samples/sec
lowlatency
7 triggers

LLstreams enable
set-config (use e.g. 00070000, 0000)
+simode
rtstatus enable
ok-1
+monitor

uspmonitor
re-boot

3.5.2 Two strong motion sensors

resetlabels
set-id
serial2
6 sensor-type (for CMG-5T)
erasefile
normal compression
0 1 bandpass
3 highpass
200 100 20 10 samples/sec
lowlatency
$77 triggers

LLstreams enable
set-config (use e.g. 00770000, 0000)
+simode
rtstatus enable
ok-1
+monitor

uspmonitor
re-boot

3.5.3 One weak motion and one strong motion sensor

When using an S6 (two-input) digitiser with both a weak motion and a strong motion instrument, the weak motion instrument must be connected as Sensor A and the strong motion instrument as Sensor B.

resetlabels
set-id
serial2
1 sensor-type (for CMG-40T)
adaptive (if desired)
erasefile
normal compression
0 1 bandpass
3 highpass
200 100 20 10 samples/sec
lowlatency
$70 triggers

LLstreams enable
set-config (use e.g. 70070000, FF00)
+simode
rtstatus enable
ok-1
+monitor

uspmonitor
re-boot