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Güralp CMG-3ESP Operator's Manual

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CMG-3ESP
Operator's Guide
Document No: MAN-ESP-0001
Issue G, February 2016
Designed and manufactured by
Güralp Systems Limited
3 Midas House, Calleva Park
Aldermaston RG7 8EA
England

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  • Page 1 CMG-3ESP Operator's Guide Document No: MAN-ESP-0001 Issue G, February 2016 Designed and manufactured by Güralp Systems Limited 3 Midas House, Calleva Park Aldermaston RG7 8EA England...

  • Page 2: Table Of Contents

    CMG-3ESP Contents Table of Contents 1 Preliminary Notes......................1 1.1 Proprietary Notice..................1 1.2 Cautions and Notes..................1 1.3 Manuals and Software................1 1.4 Conventions....................1 2 Introduction........................2 2.1 Options.....................3 2.1.1 Form factors..................3 2.1.2 Output types..................3 2.1.3 Sensor response................4 3 Installing the 3ESP....................... 5 3.1 First encounters..................5...
  • Page 3 CMG-3ESP 4.1.3 Obtaining copies of the calibration pack.........21 4.2 Calibration methods................22 4.3 Calibration with Scream!................22 4.3.1 Sensor response codes..............25 4.4 Calibration with a hand-held control unit..........26 4.5 The coil constant..................26 5 Accessories........................28 5.1 The hand-held control unit..............28 5.1.1 The meter..................28 5.1.2 Calibration..................29...

  • Page 4: Preliminary Notes

    CMG-3ESP Preliminary Notes Preliminary Notes 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...
  • Page 5 CMG-3ESP Preliminary Notes Putting these together into a single example: System prompt: user input with variable parameters MAN-ESP-0001 Issue G - February 2016...

  • Page 6: Introduction

    CMG-3ESP Introduction Introduction The CMG-3ESP is a three-axis seismometer consisting of three sensors in a sealed case, which can measure the north/south, east/west and vertical components of ground motion simultaneously. Each sensor is sensitive to ground vibrations in the frequency range 0.003 – 50 Hz, a broadband frequency response made possible by advanced force-balance feedback electronics.

  • Page 7: Options

    2.1.1 Form factors The CMG-3ESP can be supplied in several forms, besides its standard configuration: • The CMG-3ESP Compact is internally identical to the standard 3ESP, but has a different arrangement of components allowing it to fit in a smaller casing. •...

  • Page 8: Sensor Response

    CMG-3ESP Introduction A supplied breakout box connects to the sensor allowing separate connection to a power supply, recording system and hand-held control unit. As an option the 3ESP can be supplied with other output connector types, e.g. standard 26-pin D sockets, to your own pin-out specification.

  • Page 9: Installing The 3Esp

    CMG-3ESP Installing the 3ESP Installing the 3ESP First encounters 3.1.1 Unpacking The 3ESP seismometer is delivered in a single transportation case. The packaging is specifically designed for the 3ESP and should be reused 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.

  • Page 10: Connections

    CMG-3ESP Installing the 3ESP 3.1.1.2 Handling notes The 3ESP is a sensitive instrument, and is easily damaged if mishandled. If you are at all unsure about the handling or installation of the device, you should contact Güralp Systems for assistance.
  • Page 11 CMG-3ESP Installing the 3ESP You can also use the breakout box to centre the sensor masses. If your 3ESP includes the remote locking and unlocking option, you will be supplied with a slightly different breakout box with additional buttons for locking and unlocking the masses.

  • Page 12: Installation Notes

    CMG-3ESP Installing the 3ESP maintenance, in case the sensor needs to be moved and the on-site batteries no longer have sufficient charge to perform the locking procedure. 3.1.2.4 Signal output The sensors output voltages representing ground velocity on floating differential lines.

  • Page 13: Installing In Vaults

    CMG-3ESP Installing the 3ESP rejuvenation, or to study the aftershocks of a major earthquake; or the site itself may be too remote to ship in construction equipment. Temporary installations can be protected against spurious vibrations by • Selecting a suitable site •...
  • Page 14 CMG-3ESP Installing the 3ESP If you cannot easily see the pointers, you should align the sensor using the north arrow on the handle. However, the alignment of the handle with the sensors inside is less accurate than the metal pointers, so they should be used wherever possible.
  • Page 15 CMG-3ESP Installing the 3ESP Connect the sensor to the breakout box or a Güralp digitizer if you are using one. Connect a 12 V power supply either directly or through the breakout box or digitizer. If your 3ESP instrument has the standard, manual mass control system, three sockets on the casing of the 3ESP allow each mass to be locked and unlocked.
  • Page 16 CMG-3ESP Installing the 3ESP Turn the driver anticlockwise to unscrew it. After this point, you should be careful not to tilt the instrument, or you may damage it. Clean the pressure cap and apply a thin layer of molybdenum disulphide grease to the O-ring and mating surfaces.

  • Page 17: Installing In Pits

    CMG-3ESP Installing the 3ESP Ensure that the sensor cable is loose and that it exits the seismometer enclosure at the base of the instrument. This will prevent vibrations from being inadvertently transmitted along the cable. Installing in pits For outdoor installations, high-quality results can be obtained by constructing a seismic pit.
  • Page 18 CMG-3ESP Installing the 3ESP On granite or other hard bedrock , use an angle grinder to plane off the bedrock at the pit bottom so that it is flat and level. Stand the instrument directly on the bedrock, and go to step 7.

  • Page 19: Other Installation Methods

    CMG-3ESP Installing the 3ESP possible coupling to the subsoil or bedrock, which has some leeway to shift or settle beneath it. Alternatively, for the most rapid installation, place loose soil over the bottom of the pit, and compact it with a flat stone. Place the seismometer on top of this stone.

  • Page 20: Installing In Post-Holes

    CMG-3ESP Installing the 3ESP shifting due to moisture trapped between the concrete and tiling, whilst the vertical sensors show 'pings' as the tile settles. Other installations have been attempted with the instrument encased in plaster of Paris, or some other hard-setting compound (left): Again, this method produces inferior bonding to the instrument, and moisture becomes trapped between the hard surfaces.
  • Page 21 CMG-3ESP Installing the 3ESP hand-operated post-hole auger. To minimize surface effects, you should ensure that the hole is at least 1 m deeper than the length of the instrument, and preferably somewhat more. Since the hole has no lining, it may occasionally flood. However, most soil types are sufficiently permeable to allow water to soak away, leaving the packing material moist.

  • Page 22: Calibrating The 3Esp

    CMG-3ESP Calibrating the 3ESP Calibrating the 3ESP The calibration pack All Güralp sensors are fully calibrated before they leave the factory. Both absolute and relative calibration calculations are carried out. The results are given in the calibration pack supplied with each instrument: Works Order : The Güralp factory order number including the instrument, used...

  • Page 23: Frequency Response Curves

    CMG-3ESP Calibrating the 3ESP ( V / x ) ( s ) = G × A × H ( s ) In this equation • G is the acceleration output sensitivity (gain constant) of the instrument. This relates the actual output to the desired input over the flat portion of the frequency response.

  • Page 24: Obtaining Copies Of The Calibration Pack

    CMG-3ESP Calibrating the 3ESP    If you want to repeat the calibration to obtain more precise values at a frequency of interest, or to check that a sensor is still functioning correctly, you can inject calibration signals into the system using a Güralp digitizer or your own signal generator, and record the instrument's response.

  • Page 25: Calibration Methods

    CMG-3ESP Calibrating the 3ESP Calibration methods Velocity sensors such as the 3ESP are not sensitive to constant DC levels, either as a result of their design or because of an interposed high-pass filter. Instead, three common calibration techniques are used.
  • Page 26 CMG-3ESP Calibrating the 3ESP Select the calibration channel corresponding to the instrument, and choose Broadband Noise. Select the component you wish to calibrate, together with a suitable duration and amplitude, and click Inject now. A new data stream, ending Cn (n = 0 – 7) or MB, should appear in Scream!'s main window containing the returned calibration signal.
  • Page 27 CMG-3ESP Calibrating the 3ESP Pause the Waveview window by clicking on the icon. Hold down SHIFT and drag across the window to select the calibration signal and the returning component(s). Release the mouse button, keeping SHIFT held down. A menu will pop up. Choose Broadband Noise Calibration.

  • Page 28: Sensor Response Codes

    CMG-3ESP Calibrating the 3ESP [instrument-id] Serial-Nos=T3X99 VPC=3.153,3.147,3.159 G=1010,1007,1002 COILCONST=0.02575,0.01778,0.01774 CALVPC=3.161 CALRES=51000 TYPE=sensor-type RESPONSE=response-code Click OK. The script will return with a graph showing the response of the sensor in terms of amplitude and phase plots for each component (if appropriate.) The accuracy of the results depends on the amount of data you have selected, and its sample rate.

  • Page 29: Calibration With A Hand-Held Control Unit

    CMG-3ESP Calibrating the 3ESP Units Sensor Sensor type code (V/A) CMG-40T-1 or 6T-1, CMG-40_10S_100HZ 10 s – 100 Hz response CMG-40_20S_50HZ CMG-40, 20 s – 50 Hz response CMG-40_30S_50HZ CMG-40, 30 s – 50 Hz response CMG-3_30S_50HZ CMG-3T or 3ESP, 30 s – 50 Hz response CMG-40_60S_50HZ CMG-40, 60 s –...
  • Page 30 CMG-3ESP Calibrating the 3ESP The coil constant can be determined by tilting the instrument and measuring its response to gravity. To do this, you will need apparatus for measuring tilt angles accurately. Measure the acceleration due to gravity, g , at your location.

  • Page 31: Accessories

    CMG-3ESP Accessories Accessories The hand-held control unit This portable control unit provides easy access to the seismometer's control commands, as well as displaying the output velocity and mass position ( i.e. acceleration) on an analogue meter. It takes input from the 26-pin connector at the bottom, and repeats it at the connector on the side for connection to further equipment.

  • Page 32: Calibration

    CMG-3ESP Accessories 5.1.2 Calibration The hand-held control unit can be used to calibrate the 3ESP. To activate the calibration relays, turn the knob to the component you wish to calibrate, and introduce a calibration signal on the CAL SIG banana sockets.

  • Page 33: Inside The 3Esp

    1 s. CMG-3ESP sensors have no spurious resonances below 140 Hz, and weigh around 180 g. The small boom size and stiff springs allow three independent instruments to be mounted within the casing, together with all the associated feedback electronics.

  • Page 34: Automatic Control

    CMG-3ESP Inside the 3ESP The mass clamps will not secure the masses against hard knocks and jolts. The 3ESP should always be transported with at least 15 cm of foam padding. You will have received suitable packing material with the instrument.
  • Page 35 CMG-3ESP Inside the 3ESP In the five-stage process, each mass in turn is locked with a motorised micrometer (stages 1, 2, 4), and the N/S and E/W sensor bases are tilted to their end stops (stages 3 and 5). At some point during each tilting stage, the position of the relevant mass will flip to one or other side.
  • Page 36 CMG-3ESP Inside the 3ESP Again, you can use the BUSY LED to monitor the progress of unlocking. The instrument checks to see whether the vertical mass is locked, and unlocks it if necessary. The vertical mass is centred by applying pulses to the motor. This stage is often very short, since the vertical mass is locked near its central position.
  • Page 37 CMG-3ESP Inside the 3ESP position sensor indicates an offset close to zero. In the case of the horizontal sensors, the sensor frame is tilted on its base plate. Again, the controller monitors the mass position sensor and stops the centring process once it reaches its lowest offset.

  • Page 38: The Feedback System

    CMG-3ESP Inside the 3ESP The feedback system The output from a modern broadband seismometer does not depend on the natural characteristics of the instrument. Instead, the period and damping of the sensor is completely determined by a feedback loop which applies a force to the sensor mass opposing any motion.

  • Page 39: Conventional-Response Feedback

    CMG-3ESP Inside the 3ESP An active low-pass filter provides a high-frequency cut-off point at a frequency you specify. Without the filter, the velocity response is flat up to 100 Hz. Outside the feedback loop there is an active high-pass filter with a corner frequency of 0.01 Hz (100 s) or 0.005 Hz (200 s), which serves to remove any DC offsets.
  • Page 40 CMG-3ESP Inside the 3ESP MAN-ESP-0001 Issue G - February 2016...

  • Page 41: Appendices

    CMG-3ESP Appendices Appendices Appendix A - Connector pin-outs 7.1.1 Sensor and control unit output This is a standard 26-pin “mil-spec” plug, conforming to MIL-DTL-26482 (formerly MIL-C-26482). A typical part- number is ***-16-26P where the '***' is defined by the manufacturer.

  • Page 42: Breakout Box Dc Power Connector

    CMG-3ESP Appendices Wiring details for the compatible socket, ***-16-26S, as seen from the cable end ( i.e. when assembling). 7.1.2 Breakout box DC power connector This is a standard 10-pin “mil-spec” plug, conforming to MIL-DTL-26482 (formerly MIL-C-26482). A typical part-number is ***-12-10P where the '***' is defined by the manufacturer.

  • Page 43: Appendix B - Specifications

    CMG-3ESP Appendices Appendix B - Specifications Parameter Specification Hybrid sensors 0.1 – 50 Hz Velocity output bandwidth 0.01 Hz – spec * High pass filter output flat to acceleration spec – 50 Hz* High pass filter output flat to velocity Mass position output DC –...
  • Page 44 CMG-3ESP Appendices *spec refers to the quoted frequency response value, e.g. , for a “30 s” sensor, the value of spec would be 30 s = 0.033 Hz. **Temperatures below –20 °C may be accommodated with additional care. Please consult Güralp Systems for advice.

  • Page 45: Appendix C - Revision History

    CMG-3ESP Appendices Appendix C - Revision history 2000-04-28 New document 2006-02-21 Updates; added revision history 2006-11-15 Redrawn diagrams 2011-03-18 Changes to vault procedures, formatting updates 2011-08-23 Corrections to connector pin-out 2016-02-18 Corrections to connector pin-out MAN-ESP-0001 Issue G - February 2016...

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