Guralp Systems CMG-5TD User Manual

CMG-5TD Digital
Accelerometer

Operator's Guide

Document No. MAN-050-0005

Designed and manufactured by
Güralp Systems Limited
3 Midas House, Calleva Park
Aldermaston RG7 8EA
England

Proprietary Notice: The information in this document is
proprietary to Güralp Systems Limited and may be copied or
distributed for educational and academic purposes but may
not be used commercially without permission.

Whilst every effort is made to ensure the accuracy,
completeness or usefulness of the information in the
document, neither Güralp Systems Limited nor any employee
assumes responsibility or is liable for for any incidental or
consequential damages resulting from the use of this
document.

Issue D April 2013

CMG-5TD Digital Accelerometer Contents

Table of Contents

1 Preliminary Notes............................................................................................................. 4

1.1 Proprietary Notice...................................................................................................... 4

1.2 Warnings, Cautions and Notes..................................................................................4

1.3 Manuals and Software............................................................................................... 4

1.4 Conventions................................................................................................................4

2 Introduction....................................................................................................................... 5

3 Quick start.........................................................................................................................6

3.1 Unpacking and packing............................................................................................. 6

3.2 Initial check-out......................................................................................................... 7

4 Setting the gain................................................................................................................ 10

4.1 Disassembly.............................................................................................................. 10

4.2 Jumper configuration for low gain operation..........................................................11

4.3 Jumper configuration for high gain operation.........................................................12

4.4 Reassembly............................................................................................................... 12

5 Operation......................................................................................................................... 13

5.1 Installation overview................................................................................................13

5.2 Installation method..................................................................................................13

5.3 Installation in hazardous environments..................................................................14

5.4 Orientation...............................................................................................................14

5.5 Levelling................................................................................................................... 14

5.6 Power supply considerations...................................................................................14

5.7 Connections.............................................................................................................. 14

5.8 Offset adjustment.....................................................................................................15

5.9 Configuration and control using Scream.................................................................16

5.9.1 System ID.......................................................................................................... 17

5.9.2 Output control................................................................................................... 17

5.9.3 Triggering.......................................................................................................... 20

5.9.4 Baud rates.......................................................................................................... 23

5.9.5 Data flow........................................................................................................... 23

5.9.6 Buffer Memory Usage....................................................................................... 28

6 Calibration...................................................................................................................... 29

6.1 The calibration pack................................................................................................29

6.1.1 Poles and zeroes................................................................................................29

6.1.2 Frequency response curves...............................................................................30

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CMG-5TD Digital Accelerometer Preliminary Notes

6.1.3 Obtaining copies of the calibration pack.........................................................31

6.2 Calibration methods.................................................................................................32

6.3 Calibration with Scream! ........................................................................................ 32

6.3.1 Sensor response codes...................................................................................... 36

7 Connector pin-outs..........................................................................................................37

7.1 DATA........................................................................................................................37

7.2 GPS........................................................................................................................... 38

7.3 Analogue connector................................................................................................. 39

8 Specifications.................................................................................................................. 40

9 Revision History.............................................................................................................. 41

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CMG-5TD Digital Accelerometer Preliminary Notes

1 Preliminary Notes

1.1 Proprietary Notice

The information in this document is proprietary to Güralp Systems Limited
and may be copied or distributed for educational and academic purposes but
may not be used commercially without permission.

Whilst every effort is made to ensure the accuracy, completeness and
usefulness of the information in the document, neither Güralp Systems
Limited nor any employee assumes responsibility or is liable for for any
incidental or consequential damages resulting from the use of this document.

1.2 Warnings, Cautions and Notes

Warnings, cautions and notes are displayed and defined as follows:

1.3 Manuals and Software

All manuals and software referred to in this document are available from the
Güralp Systems website, www.guralp.com, unless otherwise stated.

1.4 Conventions

Throughout this manual, examples are given of command-line interactions.
In these examples, a fixed-width typeface will be used:

Example of the fixed-width typeface used.

Commands that you are required to type will be shown in bold:

Example of the fixed-width, bold typeface.

Where data that you type may vary depending on your individual
configuration, such as parameters to commands, these data are additionally
shown in italics:

Example of the fixed-width, bold, italic typeface.

Putting these together into a single example:

System prompt: user input with variable parameters

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Warning: A black cross indicates a chance of injury or death if the
warning is not heeded.

Caution: A yellow triangle indicates a chance of damage to or
failure of the equipment if the caution is not heeded.

Note: A blue circle indicates indicates a procedural or advisory
note.

CMG-5TD Digital Accelerometer Introduction

2 Introduction

The CMG-5TD consists of a fully-integrated triaxial accelerometer (CMG-5T)
and a matched 24-bit digitizer (DM-24) contained in a single, watertight
package. It is compact, lightweight, and simple to deploy. It can resolve the
full range of acceleration due to microearthquakes (0.1 uG resolution) up to
strong local earthquakes (4 g resolution).

It is provided with a combination baseplate/mounting plate, which is
separable and re-attachable, allowing for quick installation/removal and
sensor site re-occupation if necessary. The DC offsets are available at the
analogue output connector of the CMG-5TD and are user-accessible and
adjustable via adjusting screws on the top cap of the instrument. A GPS
receiver is used to provide accurate time-stamps for seismic data. The GPS
receiver is attached to the CMG-5TD via a supplied 20 metre cable.

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CMG-5TD Digital Accelerometer Quick start

3 Quick start

3.1 Unpacking and packing

The CMG-5TD accelerometer system is delivered in a single cardboard box
with foam rubber lining. The packaging is specifically designed for the
CMG-5T system. Whenever transported, the CMG-5TD system should be
packed in its original shipping container. The packaging should be saved for
re-use in the event of a later shipment.

Upon receipt of the equipment, please note any damage to the package.
Unpack on a clean surface. The package should contain: digital
accelerometer, a separable levelling baseplate, baseplate screws, concrete
anchor and mounting bolt, GPS receiver, GPS receiver cable and power/data
connection cable.

Place the CMG-5TD on a table and identify

• The power/data cable connector on the CMG-5TD top cap.

• The GPS cable connector on the CMG-5TD top cap.

• The analogue connector on the CMG-5TD top cap.

• The north orientation symbol on the CMG-5TD handle.

• The bubble level on the CMG-5TD top cap

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CMG-5TD Digital Accelerometer Quick start

• The screw on/off cover for output offset adjustment on the CMG-5TD

top cap.

• The serial number on the label, on the top or side of the instrument.

3.2 Initial check-out

This section gives a quick outline for initial system test, which should
performed prior to installation. You must provide 10-36 V DC power and a
PC running Scream.

Attach the levelling baseplate to the base of the CMG-5TD using the screws
provided. Set the CMG-5TD onto a flat surface. Using the large hex screws on
the baseplate in conjunction with the bubble level, level the instrument.
Connect the CMG-5TD directly to the PC using the supplied power/data cable

Switch on the power supply. Using the PC, start Scream and take the
following steps:

1. Click on 'Setup', from the ‘File’ menu

2. Select the ‘Com Ports’ tab

3. Click on the COM port to which the instrument is connected.

4. The factory-set baud rate for the CMG-5TD is 19200. Select 19200 from
the list.

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

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CMG-5TD Digital Accelerometer Quick start

6. In the Available Streams window, the identifier of the instrument 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)

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

8. The Stream IDs are six-character strings which uniquely identify 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. Streams with higher sample rates
will appear in the display sooner than the slower sample rates and it
might take several minutes for the status stream to appear.

9. Select the data streams in the right side of the window by clicking on
the first and then control-clicking on the last. Press the “ENTER” key
to open these streams in a new ‘Waveview’ window.

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CMG-5TD Digital Accelerometer Quick start

10. 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/receive baud rates
for each channel and the data link.

11. While viewing the time series from all three components in a
WaveView window, gently tap the CMG-5TD, and observe the response
of all three components. If the CMG-5TD passes this initial basic test,
then you may proceed to install the system (see the Operation section
of this User’s Guide).

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CMG-5TD Digital Accelerometer Setting the gain

4 Setting the gain

The built in 5T sensor has a very large dynamic range. In order to exploit the
whole of this range, two separate outputs are available, one with high gain
and one with low gain. Normally, the high gain outputs are set to output a
signal 10 times stronger than that from the low gain outputs. Only one set of
outputs – low gain or high gain – is sent to the digitiser; the selection of which
output to digitise is made using internal jumpers.

4.1 Disassembly

In order to change the gain-setting jumpers, remove the instrument's lid as
follows:

• Use a large, flat-bladed screwdriver to remove the pressure-release

screw located on the instrument's lid next to the bubble-level.

• Use a small, flat-bladed screwdriver to remove the six small screws

located around the edge of the top of the lid.

• Note the location of the lid with respect to the body. Use a pencil or

adhesive tape to mark both so that the instrument can be reassembled
in the correct orientation.

• Using a medium, flat-bladed screwdriver, gently prise the lid away

from the body. A slot is provided in the top of the cylinder for this
purpose.

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Note: To change the gain, it is necessary to open the instrument.
This work must be carried out in a clean environment in order to
prevent contamination of the mechanical components by air-borne
dust.

Caution: The CMG-5TD include components which can be
damaged by electrostatic discharge (ESD). Always work on a
properly grounded dissipative surface and wear a suitable
grounded wristband. Ground yourself by touching an earthed
conductor before handling any of the circuit boards.

Warning: GSL instruments are assembled at near to sea level.
When using the instrument at altitude, there may be a
considerable pressure differential between the air inside the
casing and the external atmosphere. This could cause the
screw to fly off with considerable force when initially
released. Take care that this does not cause injury.

CMG-5TD Digital Accelerometer Setting the gain

• Lift the lid and the attached electronics vertically out of the cylindrical

body and disconnect the ribbon cable at either end, noting the
orientation of the cable.

Looking down into the body of the instrument, you will see a small printed
circuit board mounted on an aluminium disc. This board contains the
gain-setting jumpers, which are coloured red to aid identification.

Each component (vertical, North/South and East/West) has two associated
jumpers (one for each leg of the differential connection) and these must
always be moved in pairs. It is possible to select different gains for different
channels but this is rarely desirable. Consult the markings on the printed
circuit board and the pictures below to select the desired gain.

4.2 Jumper configuration for low gain operation

Arrange the jumpers as in the picture below:

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Note: The lid-to-body seal uses 'O'-rings. Take care that the
lid does not suddenly fly off when this seal is broken.

CMG-5TD Digital Accelerometer Setting the gain

4.3 Jumper configuration for high gain operation

Arrange the jumpers as in the picture below:

4.4 Reassembly

Once the desired gain selection has been made, reconnect the ribbon cable
and gently lower the lid onto the instrument, taking care not to knock the
electronic assemblies or snag any cables. Ensure that the lid is rotated to the
correct orientation using the marks you made previously and then gently ease
it over the 'O'-ring seal and into place. Secure using the six small screws and,
finally, replace the large pressure release screw.

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CMG-5TD Digital Accelerometer Operation

5 Operation

5.1 Installation overview

These steps make up the installation procedure. Detailed instructions follow
in subsequent sections.

• Unpack the accelerometer system from the reusable container (See

quick start). Save the shipping box for possible future use.

• Prepare the mounting surface.

• Mount the levelling baseplate to the CMG-5TD.

• Orient the CMG-5TD using the orientation pointers.

• Anchor the baseplate to the mounting surface.

• Level the CMG-5TD.

• Install the GPS receiver providing a clear view of the sky, and connect

it to the CMG-5TD using the GPS cable.

• Connect the CMG-5TD to a PC running Scream

• Connect the power supply (12 to 36 V DC) to the grey/blue power/data

cable

• Switch on the power and view the acceleration time series using

Scream.

• Using a DVM, check and adjust the CMG-5TD offsets if required.

• Cover the sensor with a polystyrene cover for long term thermal

stability. The cover will act as a thermal shield from draughts.
Position the polystyrene box carefully so that it does not touch the
sensor package.

5.2 Installation method

The surface should have a scribed north/south orientation line accurately
surveyed from reliable markers. Mount the concrete anchor into the
mounting bench, around the middle of the orientation line. Loosely attach
the mounting (lower) portion of the levelling plate to the concrete anchor,
using the bolt provided. Attach the upper portion of the levelling plate to the
base of the CMG-5TD using the screws provided. Finally, attach the CMG-5TD
to the mounting base by joining the two portions of the levelling plate using
the socket-cap screws provided.

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