Serial Numbers for six-channel digitisers

Overview

Güralp DM24 digitisers are available in three-channel and six-channel versions. (Both actually have an additional full-specification input channel so you may also see them referred to as four-channel and seven-channel units.)

A six-channel DM24 can be configured to appear either as a single six-channel system, with a single System ID and Serial Number (used to identify the streams), or as two virtual three-channel digitisers, sharing a single System ID but with two separate, distinct Serial Numbers. The only differences between the two modes are the names of the resulting output streams.

This document explains how to configure each of the modes and how to switch between them.

Stream naming

GCF output streams are identified by Stream IDs, which are composed from four elements:

The System ID, which is user-programmable;
The Serial Number, which is user-programmable;
The Component ID, which identifies the component (Vertical, North/South, East/West) from which the stream originates; and
The Tap Number, which relates to the sample rate and the decimation tree (the way in which the initial high sample rate is reduced by successive division to the wanted output rates).

These are combined as shown below:

For more information about Stream IDs, including some of the more unusual variants, please see the document Stream IDs explained.

Single serial-number mode

In single serial-number mode, the first attached triaxial sensor (SENSOR A) gets allocated even tap numbers and the second attached triaxial sensor (SENSOR B) gets allocated odd tap numbers.

The first (fastest) tap outputs, therefore, have Stream IDs ending in Z0, N0 and E0 for SENSOR A and Stream IDs ending in Z1, N1 and E1 for SENSOR B. Similarly, the second (next fastest) tap outputs have Stream IDs ending in Z2, N2 and E2 for SENSOR A and Stream IDs ending in Z3, N3 and E3 for SENSOR B.

To select single serial-number mode, right-click on the digitiser’s icon in Scream! and select Terminal from the context menu. When the terminal window opens, enter the following commands, providing the desired System ID and Serial Number when prompted:

The RESETLABELS command clears dual serial-number mode, if set. It also clears any customised Component IDs, which are not described in this document.
The SET-ID command prompts for new values for the System Identifier (System ID) and Serial Number:
- The system identifier that you supply should contain between one and five alphanumeric (0-9, A-Z) characters. Alphabetic characters should be entered in upper-case.
- The serial number that you supply must contain exactly six alphanumeric (0-9, A-Z) characters and should end with two zeros ('00'). Alphabetic characters should be entered in upper-case. The first four characters are used when generating Stream IDs. The final two characters are used for customised Component IDs, which are not described in this document (but you can see here for details). If you wish to use an ID which is shorter than four characters, pad it with leading zero ('0') characters.
The system responds by printing the new system identifier and serial number, the sensor type and the “ok” prompt (which is now derived from the new serial number). If the sensor type has not been set, the word NOTSET is printed in its place.
The RE-BOOT command re-starts the system using the newly set IDs. It first asks for confirmation: key y in response.

A typical session looks like this (where “SYS0” is the old System ID, “DM24” is the new System ID and “C902” is the new Serial Number):

ok_SYS0 RESETLABELS ok_SYS0 SET-ID System Identifier ? {ALPHA} DM24 Serial # ? (SYS000) C90200 DM24 C90200 CMG-3T ok_C902 RE-BOOT Confirm with 'y' ? Y

InfoBlocks and Calvals in single serial-number mode

When working in single serial-number mode, entries in InfoBlocks and calvals.txt should be prepared as follows:

Serial-Nos - This is a free-format memo field so you may put anything you wish into it. Güralp recommend putting the two instrument serial numbers here.
VPC - This field should be populated with six comma-separated entries, corresponding to the digitiser calibration values for Z, N/S and E/W of SENSOR A, then the values for Z, N/S and E/W of SENSOR B.
G - This field should be populated with six comma-separated entries, corresponding to the instruments' calibration values in the order given above.
COILCONST - This field should be populated with six comma-separated entries, as described above.
CALRES - This field should be populated with two comma-separated entries, corresponding to the two calibration resistor values for the two instruments.
TYPE - This is a free-format memo field so you may put anything you wish into it. Güralp recommend putting the two instrument models here.
RESPONSE - This field should be populated with two comma-separated entries, corresponding to the two response codes for the two instruments. Because response codes contain spaces, each code should be double-quoted, as in the example below.
GRAVITY - This field should be populated with a single value; the local acceleration due to gravity.

Here is an example for a digitiser with a 3T seismometer as SENSOR A and a 5T accelerometer as SENSOR B. Spaces have been used to increase legibility.

[DM24-C902] Serial-Nos=T3X99, T5585 VPC=2.013,2.028,2.036, 2.030,2.019,2.024 G=1010,1007,1002, 0.256,0.255,0.255 COILCONST=0.01769,0.01778,0.01774, 1,1,1 CALRES=51000,1 TYPE=3T, 5T RESPONSE="CMG-3_30s_50Hz Vel", "CMG-5_100Hz Acc" GRAVITY=9.81089

For more information about InfoBlocks, please see the page Information blocks from Güralp digitisers. For more information about Calvals, please see the Calibration data section of the Scream manual.

Dual serial-number mode

In dual serial-number mode, the two sensors share a System ID but each has its own, distinct serial number. All tap identifiers are even.

The first (fastest) tap outputs, therefore, have Stream IDs ending in Z0, N0 and E0 for both SENSOR and SENSOR B. Similarly, the second (next fastest) tap outputs have Stream IDs ending in Z2, N2 and E2 for both SENSOR and SENSOR B.

This arrangement allows stream identifiers such as:

SITE1-VEL0Z0
SITE1-VEL0N0
SITE1-VEL0E0
SITE1-ACC0Z0
SITE1-ACC0N0
SITE1-ACC0E0

to be produced simultaneously from a single digitiser, which can be used to create more easily-recognisable stream IDs.

To select dual serial-number mode, right-click on the digitiser’s icon in Scream! and select Terminal from the context menu. When the terminal window opens, enter the following commands

The SET-ID command prompts for new values for the System Identifier (System ID) and the Serial Number for the first sensor (SENSOR A):
- The system identifier that you supply should contain between one and five alphanumeric (0-9, A-Z) characters. Alphabetic characters should be entered in upper-case.
- The serial number that you supply must contain exactly six alphanumeric (0-9, A-Z) characters and should end with two zeros ('00'). Alphabetic characters should be entered in upper-case. The first four characters are used when generating Stream IDs. The final two characters are used for customised Component IDs, which are not described in this document (but you can see here for details). If you wish to use an ID which is shorter than four characters, pad it with leading zero ('0') characters.
The system responds by printing the new system identifier and serial number, the sensor type and the “ok” prompt (which is now derived from the new serial number). If the sensor type has not been set, the word NOTSET is printed in its place.
The SERIAL2 command prompts for the second Serial Number. The serial number that you supply must contain exactly four or exactly six alphanumeric (0-9, A-Z) characters. If you enter six characters, the final two should be zeros ('00'), as described above.
The RE-BOOT command re-starts the system using the newly set IDs. It first asks for confirmation: keyy in response.

A typical session looks like this (where “SITE1” is the new System ID and “VEL0” and “ACC0” are the new Serial Numbers):

SET-ID System Identifier ? {ALPHA} SITE1 Serial # ? (C90200) VEL000 SITE1 VEL000 CMG-3T ok_VEL0 SERIAL2 Secondary Serial # {0} ? 6 characters : ACC000 ok_VEL0 RE-BOOT Confirm with 'y' ? Y

InfoBlocks and Calvals in dual serial-number mode

When working in dual serial-number mode, prepare InfoBlocks and calvals.txt exactly as if you had two separate three-channel DM24s with the same System ID but different serial numbers, as in the following example:

[SITE1-VEL0] Serial-Nos=T3X99 VPC=3.153,3.147,3.159 G=1010,1007,1002 COILCONST=0.01769,0.01778,0.01774 CALVPC=3.161 CALRES=51000 TYPE=CMG-3T RESPONSE=CMG-3_30s_50Hz Vel GRAVITY=9.80122 [SITE1-ACC0] Serial-Nos=T5585 VPC=2.013,2.028,2.036 G=0.256,0.255,0.255 COILCONST=1,1,1 CALRES=1 TYPE=CMG-5T RESPONSE=CMG-5_100Hz Acc GRAVITY=9.80122

For more information about InfoBlocks, please see the page Information blocks from Güralp digitisers.
For more information about Calvals, please see the Calibration data section of the Scream manual.