Guralp Systems CMG-DM24 User Manual

CMG DM24 DIGITISER

OPERATOR’S GUIDE

Operator’s Guide

DM-24 Digitiser

DESIGNED AND MANUFACTURED BY:

GÜRALP SYSTEMS LIMITED

3 MIDAS HOUSE

CALLEVA PARK

ALDERMASTON

READING

BERKS, RG7 8EA

ENGLAND

Telephone: [phone]

Fax: [phone]

PROPRIETARY NOTICE

The information in this Manual is proprietary to Güralp Systems Limited and may not be copied or distributed outside the approved recipient’s organisation without the approval of Güralp Systems Limited.

Güralp Systems Limited shall not be liable for technical or editorial errors or omissions made herein; nor for incidental or consequential damages resulting from the furnishing, performance, or use of this material.

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CONTENTS

			page
1.	Introduction		5
2.	Operating Instructions		9
	2.1 Stand-Alone CMG-DM24 Front Panel Connectors		9
	2.2 CMG-DM24 Sensor Module Connectors		11
	2.3	Quick Start	12
	2.4	FLASH Memory Upgrade	16
3.	Digitiser Configuration and Control Mode		19
	3.1	Digitiser Configuration:- Using SCREAM	20
		Digitiser Configuration	20
		Digitiser Output Control Programming	22
		Programming Trigger Parameters	25
		Setting Digitiser Communication Parameters	27
		Sensor Calibration	28
		Sensor Mass Control	29
		Auxiliary (Mux) Channels	30
		Buffering – Data Storage	31
		Buffering – FLASH Data Storage	31
	3.2	Digitiser Configuration:- Using Terminal	33
		Digitiser Configuration	33
		Digitiser Output Control Programming	34
		Programming Trigger Parameters	36
		Setting Digitiser Communication Parameters	37
		Sensor Calibration	38
		Sensor Mass Control	39
		Auxiliary (Mux) Channels	39
4.	Status Information		41
5.	Digitiser Data Acquisition and Telemetry		47
6.	Adding a Digitiser Module onto a Broadband Sensor		49
7.	System Power Requirements		51
8.	Description of the Broadband Digitiser		53
9.	Data Transmission Protocol & Data Block Structure		57
10.	STA/LTA Trigger Options		61
11.	GPS Receiver		69
12.	Connector Pin outs		71
13.	CMG-DM24S12, 12 Channel Digitiser.		77

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1. INTRODUCTION

The Guralp CMG-DM24 24-bit digitiser can be supplied in many different formats. The main internal features are common to them all, but they can be interfaced in different forms depending upon customer requirements. The two main types are the module, which is fixed to, and becomes a physical part of a Guralp seismometer; and the standalone digitiser, both pictured below. A 12 Channel version, the CMG-DM 24S12 Digitiser is introduced in the last section of this document.

The CMG-DM24 digitiser module can be supplied with, or to retro-fit to any of the Güralp Broadband Seismometers (CMG-1T, CMG-3T, CMG-3ESP, CMG-40T or CMG-5T). The clean, isolated and stable sensor environment is ideal for the precision low-noise requirements of a wide range digitiser. Once converted to digital form the

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output of the sensor cannot be contaminated and is easily processed, stored and transmitted over long data links.

The stand-alone configuration with (differential) analogue inputs can interface with other sensor systems.

There are two different types of housings used for the stand-alone DM24 digitiser. The water proof housing introduces in 2003 is shown below. The operation of the digitiser is identical to those digitisers used prior to 2003. The housing of the digitiser is from high impact copolymer polypropylene with external inputs mil.spec connectors fitted on to a metal plate. The digitiser housing also has internal cable storage facility.

Stand-alone configurations are supplied within a portable waterproof housing as shown in the photograph above or optionally in a 19” rack mounted enclosure. In both cases the digitiser units are fitted with high impedance low noise differential input preamplifier modules.

The stand-alone CMG-DM24 unit input connections are identical to the output connections of the Guralp CMG-1T, CMG-3T, CMG-3ESP and CMG-40T. Indeed other sensors can also be wired to the CMG-DM24.

The purpose of creating a compatible connection between the CMG-DM24 and CMG sensors is to ensure that all the broadband seismometer commands can be initiated through the CMG-DM24 module.

Generally the CMG-DM24 module has 1 to 3 analogue to digital converters with 24-bit resolution. However, the CMG-DM24 stand-alone units can have 3 or 6 digitiser channels with 24-bit resolution. There are no operational differences between the 3 channel and 6 channel CMG-DM24 systems.

ENVIRONMENTAL CHANNELS

An optional 16 channel 16 bit digitiser module can be included in the main digitiser unit to provide low sample rate data (4 s/s) primarily used for ‘State of Health’ monitoring e.g. sensor mass position, temperature, pressure, battery voltage etc. This data is packaged and processed in exactly the same fashion as the primary digitiser channels.

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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

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broadband digitiser. The operational features of both systems are identical with identical command and control functions.

The CMG-DM24 units manufactured for borehole applications are described in the borehole sensor operator’s manual.

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2.OPERATING INSTRUCTIONS

2.1STAND-ALONE CMG-DM24 FRONT PANEL CONNECTORS

TOP PANEL & CONNECTORS ON STAND-ALONE DIGITISER

(DM24-S6 SHOWN)

PANEL & CONNECTORS ON STAND-ALONE DIGITISER

(DM24-S6 SHOWN)

Sensor A (Sensor B):- CMG-DM24-S3 has one 26 way Mil-Spec sensor input plug, while the CMG-DM24-S6 has two (sensor A and sensor B as shown in the diagram at the front of this section). Each sensor input (as with the 19inch rack mount model) have high impedance differential inputs. The sensor inputs carry sensor power and three channels of differential velocity, mass and calibration signals (see pin-out table in the Appendices).

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Data:- 10 pin Mil-Spec plug for digitiser power, receive and transmit digital data

GPS:- 10pi Mil-Spec plug. Carries power supply to the GPS, receive and transmit data, and 1 pulse per second reference signal.

Auxiliary:- Optional eight 16 bit, 4 samples per second channels primarily for ‘state of health’ monitoring, e.g. sensor mass position, external temperature, pressure, battery voltage.

POWER SUPPLY REQUIREMENTS

The CMG-DM24 unit operates from a wide input voltage range of 10 to 36 Volts DC. The power consumption for the portable surface unit is:

CMG-DM24 - 3 Channel-115mA from 12 Volts

CMG-DM24 - 6 Channel-145mA from 12 Volts

CMG-GPS1-190mA from 12 Volts

CMG-GPS2-75mA from 12 Volts

The given power supply current requirements are a guideline. There are many factors which can influence the power consumption of the sensor system, for this reason it is recommended that the user should budget more generously when choosing power supplies than the given typical values.

The listed power supply consumptions should be checked against the supply requirements given in the calibration documents.

NOTE

A dc-dc converter is used within each module of the system (sometimes more than one dc-dc converter is used within a module) and it is generally recognised that the start up current of such dc-dc converters can be a factor of 5 to 8 times larger than the quiescent currents given above.

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2.2 CMG-DM24 SENSOR MODULE CONNECTORS

Air Pressure

Level relief screw

Bubble

10 pin Mil-Spec	10 pin Mil-Spec
Data output and	GPS input
power input

OPTIONAL

26 pin Mil-Spec plug analogue output of

The diagram above shows the lids for the digitiser module that is fixed to a Guralp sensor (CMG-1T, CMG-3T, CMG-3ESP, CMG-40T or CMG-5T).

Data:-10 pin Mil-Spec plug for power supply to the digitiser and sensor, digital transmit and receive data.

GPS:- 10 pin Mil-Spec plug. Carries power supply to the GPS, receive and transmit data, and 1 pulse per second reference signal.

Analogue:- This is a customer requested option. The 26 pin Mil-Spec plug carries the analogue signals directly from the attached sensor below and is the analogue input for the optional eight 16 bit digitiser channels.

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2.3 QUICK START

1.Connect the GPS cable to the digitiser’s plug marked ‘GPS’ (GPS is not essential for initial test set-up).

2.The other cable supplied with the module or stand-alone digitiser has one 10 pin Mil-Spec socket at one end to connect to the digitiser connector marked ‘Data’. This cable splits into two; one part has a 9 pin ‘D’-type socket to connect to the COM port of a PC, the other part of the cable is connected to a 11-36V power supply.

3.Install SCREAM software (see later chapter) on your PC and run.

4.To configure the COM port connected to the digitiser, start from the main window in SCREAM:-

6.Click on the ‘File’ button , select ‘Setup’

7.Select the ‘Com Ports’ tab

8.Click on the COM port to which the Digitiser is connected.

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9.Select ‘Autodetect’

SCREAM will detect, then display the baud rate that the digitisers output is currently set at.

10.Click on the ‘OK’ button to return to the main Available Streams window.

11.In the Available Streams window the identifier of the digitiser will appear in the left hand frame (which appears similar to the tree type format of Windows Explorer) under:-

Network >

Local >

Com1’ (if Com1 is used)

12.The data streams will appear in the right-hand frame.

13.The Stream ID’s are six character strings uniquely identifying each instrument, component and sample rate. (There may be up-to four different sample rates per channel)

The stream ending in ‘00’ contains status information from the digitiser. Depending upon the selected sample rate, then the streams with the higher sample rates will appear in the display sooner than the slower sample rates.

14.If a digitiser module is running then the format will most likely be 16 or 32 bit format as indicated in the Available Streams window, due to the seismic data.

15.If a Stand-Alone digitiser is running, then an analogue seismic instrument can now be connected to a Sensor Input port.

16.From the main ‘Available Streams’ window,

click on the ‘Windows’ button,

choose ‘New WaveView Window’ to create a WaveView window for displaying the data.

17.Select the data streams in the right side of the window and drag them into a ‘Waveview’ window.

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18. SCREAM will now display digitised data in the ‘Waveview’ window.

Above is shown a basic WaveView window showing one 3 component instrument.

The screenshot below shows more of the power and flexibility of SCREAM. Some networked instruments can be seen in the Available Streams window with some of their output traces shown in the WaveView.

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19.To see status information coming from the digitiser, right click on the status stream, from the pop-up menu select ‘View’. A new window, ‘Status’ should open containing text. The first blocks will give the boot message from the DM, including its software revision and the data streams selected for down-loading and triggering. Later blocks give information on the expected GPS satellites, the location of the GPS antenna, time synchronization status and transmit and receive baud rates for each channel and the data link.

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2.4 FLASH MEMORY UPGRADE

For the later models with Flash memory it is possible for the user to upgrade the digitiser software.

Guralp Systems have a mailing list to keep Scream users up to date. To subscribe, send an email to [e-mail] with a single line in the body containing "subscribe screamusers" (without the quotes). This will keep the users informed of latest upgrades available.

To find out what the users current software version is, either double click on the digitiser icon in the main Start-up window and the Configuration Setup window will open up, or right click on the icon and select Configure from the pop-up menu for the same Configuration Setup window. The picture below shows “Software revision v.091”.

First obtain the latest software, then proceed as the following instructions.

1)In SCREAM’s main startup window, right click on the digitiser icon and select Terminal from the pop-up menu. This will open as shown

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2)If the user presses the Enter key “ok” will appear on a new line, signifying that there is two-way communication with the digitiser.

3)Re-boot the digitiser by turning the power off then on again and the initial bootup information will be displayed similar to that shown in the picture below.

4)In the instance shown above, the user then has 13 seconds to type “h8upload” then press enter. After the next message “Ready to upload” appears, as shown below, right click anywhere on the terminal window and select send file from the pop-up menu.

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5)Through your computer’s directories find the file to be uploaded and click on it, or type in the full path and file name to display it in the File name edit box, then click on the Open button.

Whilst the file is loading a countdown window as shown below will be on display.

6)Re-boot the digitiser by switching off and on, for the new program to install.

7)Finally, once the instrument has finished automatically backing-up the old and new firmware, reboot the unit and the firmware will be installed.

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3. DIGITISER CONFIGURATION AND CONTROL MODE

A digitiser may be reprogrammed using the SCREAM configuration setup interface. For any given digitiser, this interface module may be accessed by double-clicking with the right mouse button on the digitisers icon in the Available Streams window. If you single-click on the digitisers icon with the left mouse button, you must select Configure from the pop-up menu. Using this module of SCREAM, you may interactively set the digitisers system characteristics, control the output of streams at different digitisation rates, turn on or off the output from the low digitisation rate multiplex channels (Mux Channels), set output baud rates and digitiser buffering parameters, as well as invoke seismometer calibration.

Using any standard terminal program such as Hyperterm or Kermit, these parameters may also be changed by sending text commands to the digitiser. This mode may also be invoked from SCREAM by single-clicking on the digitisers icon with the right mouse button and selecting Terminal from the pop-up menu. When using standard terminal programs, you must initiate command mode by typing Control-S when in the text mode. This is done automatically by SCREAM when a terminal window is opened to a digitiser. If you use the SCREAM configuration set-up interface, data collection will continue while you are setting digitiser parameters. If you use SCREAM’s terminal mode or another standard terminal program, data collection will be interrupted until you exit terminal mode by issuing a re-boot command.

Parameters from most of the commands are stored to the battery-backed CMOS and only take effect when the digitiser is rebooted. Some seismometer control commands, such as unlocking and calibration take place immediately. When you click the Download button from the digitiser configuration set-up interface, the parameters you have chosen are transferred to the digitiser and it is automatically rebooted. You will notice a data gap in the Waveview window corresponding to the digitiser you have rebooted. This occurs because the reboot automatically clears the data buffer and resets the output block counter.

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3.1 DIGITISER CONFIGURATION:-USING ‘SCREAM’

To access the digitiser configuration setup from SCREAM, double-click with the left mouse button on the digitisers icon in the Available Streams window ( NOT the Local or COM port icons). Alternatively, you can single-click on the digitisers icon with the right mouse button, then select Configure from the pop-up menu.

DIGITISER CONFIGURATION

System Identifier and Serial Number: The digitiser type is identified by its system identifier and serial number. These two parameters are stored as the first two 32-bit fields in the header of each data and status block generated by the digitiser to indicate the blocks origin. Each of these parameters consists of 6 alphanumerics encoded as base 36 numbers. On delivery from the factory, the system identifier and the serial number are, respectively, set to the GSL works order number and the DM serial number, or if bonded to a seismometer, the seismometer’s serial number. The System-ID can be reset to any convenient combination of letters and numbers, such as an abbreviation of your institution.

Sensor Type: If the sensor attached to the digitiser is a Guralp velocity sensor, several seismometer functions, such as sensor locking, centering and calibration, may be controlled through the digitiser. The type of sensor programmed with this option determines which functions will be available through the SCREAM digitiser configuration set-up interface or through interactive commands. If the digitiser is bonded to a sensor, it will arrive from the factory programmed to the proper sensor type.

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GPS Type: The digitiser can utilize time signals from different sources. Options available from GSL are Trimble GPS units (now obsolete), Garmin GPS units or stream synchronization. In stream synchronization, time signals from a GPS antenna or one of the radio time standards are sent via telemetry from a central site to the digitiser. In order to synchronize with the time standard, the correct option must be selected.

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DIGITISER OUTPUT CONTROL PROGRAMMING

The screen shot below shows the Output Control window for a CMG-DM24-S3 standalone digitiser. The digitiser module set-up will appear the same. The CMG- DM24-S6 will display an extra 3 columns (Z, N and E) on the right –hand side, corresponding to the extra three channels available on that model.

Sampling rate: The output of the digitiser’s analogue-to-digital converters (ADC) is data sampled at 2000 Hz. These data are filtered and reduced to lower rates using a digital signal processor (DSP). The DSP has 4 cascaded filter/decimation stages each of which can be programmed for decimation factors of 2, 4, 5, 8 or 10. The output of each stage is called a “tap”. The first filter stage, tap 0, is preset to reduce the data by a factor of 10 to 200 samples/second, but each of the subsequent stages may be configured for a different decimation factor.

The four windows on the left of the Output Control screen (shown above) allow you to select the sampling rates for three of the four digitiser taps. The upper window corresponds to tap 0 and has a fixed sampling rate of 200 Hz. Each of the other taps may have a sampling rate lower than its predecessor above, if the rate can be achieved by decimation by 2, 4, 5, 8 or 10. Clicking on the window shows a list of the rates that are permitted, given the sampling rate in the window above it.

If some of the outputs are not required then leave the buttons ‘unticked’ to save communications capacity.

Stream selection: The CMG-DM24-S3 has three channels or streams. These are depicted by the three columns of small windows labelled Z, N and E in the Output Control window shown above.

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A tick in a box will give an output for the corresponding channel (column) at the corresponding sample rate (row). For each sample rate there are two possible rows to tick. The upper row for each sample rate will give a continuous output at that sample rate; the lower row, shown diagrammatically as passing through a switch, will only output data when its trigger criteria are met (see below).

The Stream IDs displayed in the main Available Streams window has sixcharacter ID’s. The first four characters identify the digitiser, the last two characters identify the stream from the digitiser. The first of these two characters identify the channel, the second defines the ‘tap’, or digitiser output ( see Data Transmission Protocol & Data Block Structure later).

For example; for the Output Control configuration shown above, at the beginning of this sub-section, there will be three data streams, Z, N and E, outputing data at 100sps, 20sps and 2sps. This is shown below, where the digitiser ‘1123’ has the following streams:-

∙Z2, N2, E2 are input channels Z, N, E output through the second tap ‘2’;

∙Z4, N4, E4 are input channels Z, N, E output through the third tap ‘4’,

∙Z6, N6, E6 are input channels Z, N, E output through the fourth tap ‘6’,

∙00 is the digitiser status stream (notice no sample rate),

∙M8, M9, MA are sensor mass positions for Z, N, E channels

∙MB, ME, MF are three of the optional eight 16bit channels available

System Serial

Identifier Number

Channel & tap number

Triggered output stream selection: For each tap there are two rows of boxes where the user can tick either triggered or continuous data outputs. The digitiser applies a simple short term average (STA) - long term average (LTA) algorithm to a selected stream or set of streams to determine whether the trigger condition is met. These streams may be bandpass filtered before evaluation using standard bandpass parameters. The data transmitted due to the trigger may be from different streams than those used to determine the trigger.

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