Guralp Systems CMG-EDU User Manual

CMG-EDU

Educational Seismometer System

Op erator’s g ui de

Part MAN-EDU-0001

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

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 usage of this
material.

Issue B 2009-10-23

CMG-EDU

Table of Contents

1 Introduction...............................................................................................................4

1.1 Unpacking and handling....................................................................................4

1.1.1 Handling notes............................................................................................5

2 Installing the CMG-EDU...........................................................................................6

2.1 Installing in vaults..............................................................................................6

2.1.1 Choosing a location.....................................................................................6

2.1.2 Temperature stability..................................................................................7

2.1.3 Other considerations...................................................................................8

2.2 Setting up............................................................................................................9

3 Viewing data with Scream!.....................................................................................11

3.1 The main window.............................................................................................11

3.2 Serial ports........................................................................................................11

3.3 The stream buffer.............................................................................................13

3.4 The source tree.................................................................................................13

3.4.1 Icons...........................................................................................................14

3.5 The stream list..................................................................................................15

3.5.1 Sorting options..........................................................................................16

3.6 Waveview windows..........................................................................................17

3.6.1 Zooming in and out...................................................................................18

3.6.2 Making measurements..............................................................................18

3.6.3 Printing......................................................................................................19

3.6.4 Paused mode..............................................................................................20

3.6.5 Other icons................................................................................................21

3.7 Viewing status streams.....................................................................................21

4 Recording and playback.........................................................................................23

4.1 Recording..........................................................................................................23

4.2 Files...................................................................................................................24

4.3 Playback............................................................................................................27

4.3.1 GCF files....................................................................................................27

5 Advanced usage.......................................................................................................31

5.1 Using the command interpreter.......................................................................31

5.2 General configuration.......................................................................................32

5.2.1 SET-ID........................................................................................................32

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5.2.2 .IDS............................................................................................................33

5.2.3 BAUD.........................................................................................................33

5.2.4 GO..............................................................................................................33

5.2.5 RE-BOOT...................................................................................................34

5.3 GPS and timing systems...................................................................................34

5.3.1 XGPS..........................................................................................................34

5.3.2 HR-CYCLE.................................................................................................34

5.3.3 SET-RTC....................................................................................................34

5.3.4 TIME?.........................................................................................................35

5.3.5 .FIX............................................................................................................35

5.3.6 .POSITION.................................................................................................35

5.4 Calibration........................................................................................................36

5.4.1 SINEWAVE................................................................................................36

5.4.2 SQUAREWAVE.........................................................................................37

5.4.3 MINUTE.....................................................................................................37

5.4.4 MINUTES ?................................................................................................38

5.4.5 %AMPLITUDE...........................................................................................38

5.4.6 AMPLITUDE ?...........................................................................................38

5.4.7 RESP..........................................................................................................38

5.4.8 MASSES?...................................................................................................38

6 Troubleshooting and help.......................................................................................39

6.1 Troubleshooting................................................................................................39

6.2 Limited warranty..............................................................................................40

6.3 Contacting Güralp Systems..............................................................................40

6.4 Resources for teachers and students................................................................40

7 Connector Pinouts...................................................................................................42

7.1 Sensor Connectors............................................................................................42

7.2 Power/Data Connectors....................................................................................43

7.3 Data Connectors................................................................................................44

7.4 GPS Connectors................................................................................................45

8 Revision History......................................................................................................46

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1 Introduction

The CMG-EDU is an ultra-compact single-axis broadband seismometer
designed specifically for educational uses. It is available in either
vertical or horizontal form.

The CMG-EDU is ready to record ground movements as soon as you
provide it with power. It does not have to be unlocked or centred as
long as its base is within 3 ° of horizontal. For the best results,
however, you should install where possible on a hard, near-horizontal
surface, preferably underground. See “Choosing a location” in Section

2.1 for recommendations. Also supplied is a Güralp Systems CD24E1

compact single-component digitizer, and a GPS unit.

Each package is delivered with a detailed calibration sheet showing its
serial number, measured frequency response in both the long period
and the short period sections of the seismic spectrum, sensor DC
calibration levels, and the transfer function in poles/zeros notation.

1.1 Unpacking and handling

The CMG-EDU instrument is delivered in a single case, with specially
designed packaging. You should reuse this case whenever you need to
transport the sensor. Please note any damage to the packaging when
you receive the equipment, and unpack on a safe, clean surface. The
package should contain:

• the seismometer with attached signal cable;

• the digitizer;

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Operator's guide

• the GPS unit with attached data cable;

• a blue power/data cable;

• a calibration and installation sheet, and

• this manual.

You will need to provide your own 12–24 V DC power supply, and a
Windows or Linux PC for recording the data.

1.1.1 Handling notes

Although the CMG-EDU is relatively rugged, it can be damaged if
mishandled.

• Do not bump, kick or drop the sensor.

• Do not kink or walk on the data cable, nor allow it to bear the

weight of the sensor.

• Do not ground either of the signal lines from the instrument.

If any component is missing or appears damaged, contact Güralp
Systems immediately (see Chapter 6, “Troubleshooting and help”.)

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CMG-EDU

2 Installing the CMG-EDU

2.1 Installing in vaults

The CMG-EDU is a sensitive instrument designed to measure
extremely small movements of the ground. These movements are the
sum of all the vibrations arriving at the instrument: as well as distant
earthquakes and nearby tremors, the ground responds to surf on
nearby beaches, quarry blasts, heavy machinery, traffic, and even
people moving around the building. Temperature changes and air
currents in the same room as the sensor can also affect its output.

2.1.1 Choosing a location

When studying natural earth movements, any other effects introduce
unwanted noise into the system. It is therefore important to choose an
appropriate site for the instrument, ideally in an underground vault
with the sensor installed on a concrete pier that is in direct contact
with the bedrock.

This setup has a number of advantages:

• It is installed below ground. Most man-made noise tends to

travel along the surface, and natural microseisms (tiny natural
flexings of the Earth's crust) also occur near the surface.

• Good contact with bedrock means that the signals accurately

reflect earth motions; seismic waves do not have to travel
through layers of soft soil and sediment.

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• If the vault is inside a larger structure, its foundations are

separated from the pier, so that nearby vibrations are not
transmitted to the sensor.

A high-quality seismic vault can be incorporated into the construction
plans of a new building at relatively low cost. However, if you are not
in a position to build a dedicated vault, you can still reduce noise to a
satisfactory level by

• installing below ground, in the basement or sub-basement of an

existing building;

• placing the sensor directly on a cement floor to improve contact;

and

• locating the sensor in a quiet corner away from people and

machinery (e.g. air conditioning and heating systems, elevators,
etc.)

Installation on higher floors is not recommended, especially for
horizontal sensors, since any “give” in the floor near the sensor will
cause it to tilt slightly and register a signal.

2.1.2 Temperature stability

The CMG-EDU can operate over a wide temperature range (–10 °C to
+75 °C). However, the sensor mass is sensitive to fluctuations in local
temperature. This affects the response of the instrument at long
periods. Sunlight and other bright lights can also cause small
mechanical stresses that will be detected by the sensor. You can
minimise these effects by

• installing in a basement, where the temperature is normally

more stable than above ground;

• locating the sensor in a dark, protected corner, and

• enclosing it in an insulated box (expanded polystyrene works

very well). This also helps protect the sensor from air currents.

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CMG-EDU

2.1.3 Other considerations

• The sensor and cables should be situated well away from other

electical cables and appliances. Stray radiation from these
sources may interfere with the sensor's electronics.

• The sensor should be placed on a smooth, level surface free

from cracks. Small cracks tend to open and close slightly with
changes in humidity and temperature, causing the surface to
move slightly.

• All three of the sensor's metal feet must make good contact with

the floor.

• The signal cable from the sensor should rest loosely on the

ground nearby, so that vibrations are not transmitted along it.

• If your recording or digitizing equipment has front-panel

indicators or connectors, make sure it can be reached without
disturbing the sensor.

• The GPS unit needs to be in a location where it can see as many

satellites as possible. A location with a good view of the sky,
preferably down to the horizon, is recommended. If you are in
the Northern Hemisphere, make sure as much of the southern
sky as possible is visible. Conversely, in the Southern
Hemisphere, make sure the GPS can see a large area of sky to
the north.

The GPS unit is supplied with a 15 m cable to the digitizer.

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2.2 Setting up

Once you have chosen suitable locations for the sensor, digitizer and
GPS, you need only connect the various components and supply them
with power. The digitizer and sensor will begin working immediately.

• Connect the grey cable attached to the sensor to the SENSOR

socket on the digitizer.

• Connect the brown cable attached to the GPS unit to the GPS

socket on the digitizer.

• The remaining blue and grey cables are joined together at a 9-

pin RS232 socket. Connect this socket to your PC’s serial
connector.

• The grey cable from the RS232 connector ends in red and black

wires. Connect the black wire to the negative (–) terminal of the
power supply, and the red wire to the positive (+) terminal.

• The blue cable from the RS232 connector ends at a blue socket.

Connect this to the DATA plug on the digitizer. Do this step last
– an intermittent power supply can damage the digitizer, so it is

best to make sure the wires to the power supply terminals are
securely connected before you connect the digitizer.

• When everything is connected, the digitizer should be drawing

around 50 mA from the power supply. You can measure this
either directly from the power supply unit (if it has the facility)
or by connecting a 5 W-rated, 1 Ω resistor in series with the
positive terminal and measuring the voltage drop across it: 50

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CMG-EDU

mA through a 1 Ω resistor should consume 50 mV.

If the digitizer draws significantly more or less than 50 mA,
switch it off immediately and contact Güralp Systems.

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Operator's guide

3 Viewing data with Scream!

You can use Güralp Systems' Scream! software to view incoming
seismic data, record it, and play events back later. Windows and Linux
versions of Scream! are freely available from Güralp Systems.

3.1 The main window

When you start Scream!, you will be shown an empty main window:

Scream! is now ready for you to start adding data sources.

3.2 Serial ports

1. Select File Setup...→ . If the Com Ports tab is not visible, bring it
to the front.

If you are running Scream! for the first time, it will
automatically bring up this window, together with a short
tutorial.

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CMG-EDU

You can also configure a serial port by right-clicking on its entry
in the streams list (the left-hand panel in the main window) and
selecting Configure... However, you can only do this if data has
already arrived through the port, making it appear in the
streams list.

2. The serial ports available to Scream! are listed in the table.
Identify each port, and the instrument connected to it.

If you are using Microsoft Windows, the Port number
corresponds to the COMn number of the serial port.

If you are using Linux, Port numbers 1 – 64 refer to the built-in
serial ports /dev/ttyS0 – /dev/ttyS63, and 65 and above to
USB-connected serial ports beginning /dev/ttyUSB0.

A port may not be listed if it is not installed, or suitable drivers
are not available, or if another program is using it. Scream!
scans your computer for new ports each time you open the
Setup window. To make Scream! scan the ports again, click the
Port column heading.

3. Configure each port according to the settings of the instruments
connected to them:

Baud Rate : The speed of the serial link to the instrument. If you
do not know the baud rate of your digitizer's output port, select
Auto-Detect from the drop-down menu to have Scream! attempt
to detect it for you. The instrument must be producing data for
this to work.

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Operator's guide

You can set all ports to the same baud rate by clicking on the
column heading and choosing a suitable value from the drop­down menu.

Under normal conditions, you will not need to change any of
the remaining settings.

4. Click OK.

Streams from connected instruments should now begin appearing in
the right-hand portion of Scream's main window.

Scream! will remember all the data sources you have specified on exit.
When you next open the program, it will automatically try to re­establish all the connections.

3.3 The stream buffer

Scream! works by recording incoming streams into a fixed area of
memory, called the stream buffer. All of Scream!'s operations work
with the data in this buffer.

When you start Scream! for the first time, this buffer is empty. You can
add data to it either by receiving it from local serial ports, connecting
to Scream! network servers, or replaying GCF files.

Once the stream buffer is full, Scream! will start discarding the oldest
data. If you have not told Scream! to record the incoming streams (see

Chapter 4, “Recording and playback”), then you will not be able to get

discarded data back.

If you have enabled GCF recording, Scream! keeps track of the files
which contain data in the stream buffer, and saves this information in
a .lst file in the current recording directory. When Scream! is
restarted, it reads this file and tries to rebuild the stream buffer as it
was when it was shut down. Otherwise, the buffer starts off empty as
before.

3.4 The source tree

The tree in the left panel of the main window shows all the data
sources currently connected to Scream!.

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Scream!'s source tree has two main parts: Files, which contains all the
files you have replayed (including automatic replay: see Section 4.3,

“Playback”), and Network, which represents your seismic network.

Beneath Network is a list of all the network servers Scream! is
connected to, plus the entry Local for your computer's own serial
ports.

The next layer contains the serial ports themselves. These icons are
provided to help you identify the instruments, as well as providing
direct terminal access.

You can tell Scream! to ignore a particular instrument by right-clicking
on its icon and selecting Ignore. When you do this, Scream! will
discard any blocks it receives from the instrument. They will not
appear in the stream buffer or be recorded to disk. Select Ignore again
to stop ignoring the instrument.

3.4.1 Icons

Instrument icons change colour to provide you with a quick overview
of the instrument's timing and mass position status:

If both halves of the instrument icon are clear , Scream! has not
received any information from the instrument since the program
started.

If the top half is green , the instrument has reported a satisfactory
timing fix.

If the top half is yellow , the instrument has reported a gap in the
timing stream. This will occur if the GPS signal deteriorates to the
point where the receiver cannot keep a lock on the satellites.

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