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Guralp Systems 3TB Operator's Manual

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Güralp 3TB
Operator's Guide
Document No. MAN-BHO-0001
Issue G, November 2019
Designed and manufactured by
Güralp Systems Limited
3 Midas House, Calleva Park
Aldermaston RG7 8EA
England

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  • Page 1 Güralp 3TB Operator's Guide Document No. MAN-BHO-0001 Issue G, November 2019 Designed and manufactured by Güralp Systems Limited 3 Midas House, Calleva Park Aldermaston RG7 8EA England...

  • Page 2: Table Of Contents

    3.4 Operating the hole-lock...................17 3.4.1 Disengaging the hole lock................18 3.5 The surge suppressor sonde...................20 3.6 Using Baffles......................21 4 Installing the 3TB in a borehole..................22 4.1 Installing a sensor with hole lock unit..............22 4.2 Installing a sensor using sand backfill..............26 4.2.1 Procedure......................27 4.3 Assembling the winch....................31...
  • Page 3 5.1.2 Frequency response curves................53 5.1.3 Obtaining copies of the calibration pack............54 5.2 Calibration methods....................54 5.3 Calibration with Scream!..................55 5.3.1 Sensor response codes for 3TB instruments..........58 5.4 Calibration with a hand-held control unit..............58 5.5 The coil constant.....................58 6 Inside the 3TB.......................60 6.1 The sensors......................60...

  • Page 4: Preliminary Notes

    Güralp 3TB 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.

  • Page 5: Introduction

    Güralp 3TB Introduction 2 Introduction The Güralp 3TB is a three-axis seismometer consisting of three sensors stacked vertically in a sealed borehole sonde, designed for use in cased boreholes with diameters between 99 mm (≈3.9 “) and 203 mm (≈8 “). The seismometer system is self-contained except for its 12 –...

  • Page 6: System Configuration

    • breakout box to perform installation and maintenance tasks. For example, a borehole or pit installation of a 3TB or 3ESPB instrument with single- jaw hole lock has the following layout: MAN-BHO-0001...

  • Page 7: Digital Borehole Installations

    In this case no hole lock unit is necessary. The 3V sensor is identical to the vertical-component module of the 3TB instrument, allowing you to build mixed arrays of 3V and 3TB sensors with identical response characteristics. 2.2 Digital borehole installations The Güralp DM24 digitizer is available in a borehole sonde form.

  • Page 8: The Hole Lock System

    26-pin “RECORDER” socket of the breakout box. 2.3 The hole lock system The hole lock clamp unit in a 3TB instrument provides a stable platform for the sensor modules mounted above and below it. It is designed to maintain a positive pressure on the borehole casing over a prolonged period of time without attention, and to fix the sonde in place whilst avoiding transmitting any stresses.
  • Page 9 Güralp 3TB Introduction the locking jaw pushes two steel skids against • the side of the borehole, providing two line contacts; only the tips of the skids come into contact • with the borehole, providing three point contacts; a single skid is combined with a pad to provide •...

  • Page 10: The Three-Jaw Hole Lock

    Güralp 3TB Introduction The motor has a power system separate from that of the sensor, and can be controlled from the surface using a hole lock control unit. Once the sonde is installed, the hole lock control unit may be removed. Without power, the hole lock will not be able to retract, and the sensor will be secured.

  • Page 11: First Encounters

    3.2 Handling notes The 3TB is a sensitive instrument, and is easily damaged if mishandled. It will not stand vertically upwards without support, and should not be operated until it has been securely installed in a borehole casing. If you are at all unsure about the handling or installation of the device, you should contact Güralp Systems for...

  • Page 12: Control Units

    • 3.3 Control units The 3TB is operated from the surface through various control units. All the 3TB's functions can be accessed through one or other unit. Most can be removed from the site once the instrument is ready for use.
  • Page 13 Instruments with active-high calibration can be manufactured on request. 3.3.1.2 Mass locking and unlocking The 3TB is delivered with its sensor masses locked, so that they will not be damaged in transit. You should lock the masses whenever you need to move the instrument.

  • Page 14: The Hand-Held Control Unit

    Güralp 3TB First encounters microcontroller will free the vertical, N/S and E/W sensor masses in turn and ready them for use. Once this is done, the controller automatically starts a centring cycle. If you issue an UNLOCK command when the masses are already free, the instrument will attempt to lock the masses first, and then unlock them in sequence as normal.
  • Page 15 CALIBRATION SIGNAL inputs. The CAL ENABLE dial must be set to 'V' – the 3TB has only one calibration enable line and this acts on all components simultaneously. The sensor's response can now be monitored or recorded, and calibration calculations carried out.

  • Page 16: The Inclinometer Monitor Unit

    First encounters 3.3.3 The inclinometer monitor unit All 3TB borehole sensor systems can operate successfully in boreholes with tilt angles of up to 3.5° from the vertical although instruments which can operate at tilts of up to 12° are available – please contact Güralp Systems for details. To check that the instrument is installed suitably close to the vertical, a two-axis inclinometer is installed within the sensor housing.

  • Page 17: Operating The Hole-Lock

    Güralp 3TB First encounters the sensor masses. Instead, if possible, you should move the instrument within the borehole to a place where it can lie closer to vertical. If you need to use the outputs of the inclinometer for some other purpose, you can also connect a multimeter to the banana sockets on the inclinometer monitor unit.

  • Page 18: Disengaging The Hole Lock

    Güralp 3TB First encounters Engaging the hole lock To extend the jaw of the hole lock: 1. Hold the switch on the hole lock control unit in the EXTEND JAW or + position. If you are using a deep-borehole control unit, there will be an additional dial compared to the unit pictured;...

  • Page 19: The Surge Suppressor Sonde

    The surge suppressor sonde has the same connector as the instrument on its top face and a short, permanently attached cable extending from the bottom, which connects directly to the 3TB. Internal electronics provide a high degree of protection from damage cause by electrical surges, as can arise during, for example, a nearby electrical storm.

  • Page 20: Using Baffles

    Güralp 3TB First encounters 3.6 Using Baffles Baffles are a useful tool to prevent convection currents in the borehole from generating low-frequency oscillations. The baffle consists of some large, deformable washers and spacer material attached to a cable clamp. For best results, one should be installed on the signal & suspension cable, half way between the sensor and the surge arrestor.

  • Page 21: Installing The 3Tb In A Borehole

    Güralp 3TB Installing the 3TB in a borehole 4 Installing the 3TB in a borehole Before installing any instrument in a borehole, you should prepare the installation site. Clean the area around the borehole head, so there is clear access all around it.
  • Page 22 Güralp 3TB Installing the 3TB in a borehole If applicable, you should test the hole lock mechanism before installing the sensor. For safety reasons, the hole lock is normally supplied with the arm extended. To test the mechanism, connect the signal...
  • Page 23 Güralp 3TB Installing the 3TB in a borehole Attach the lifting loop to the sensor using four M5×16 screws (provided). Join the loop to the bottom of the strain relief mechanism or surge- suppressor sonde using the linking cable provided.
  • Page 24 17. Fix the sensor system into the borehole using the hole lock arm (see Section 3.4 on page 17). Note: If you are installing a 3TB in a deep borehole, the weight of the sensor will stretch the load bearing cable slightly.

  • Page 25: Installing A Sensor Using Sand Backfill

    Güralp 3TB Installing the 3TB in a borehole 18. Use the winch to drag the assembly up within the borehole for a distance of 15 to 30 centimetres. This will ensure that the hole lock arm and the skids or studs on the sonde keep the sensor package vertical within the borehole. Do not drag too far, or you will damage the contact points.

  • Page 26: Procedure

    Güralp 3TB Installing the 3TB in a borehole The following photographs show the steps involved in backfilling with sand:                   4.2.1 Procedure To install a sensor at the bottom of a borehole of known depth using sand backfilling: Measure or calculate the physical volume of the unit which is to be installed in the borehole.
  • Page 27 Güralp 3TB Installing the 3TB in a borehole times during tightening in order to ensure that the connector is screwed fully home. If your system does not have a separate surge-suppressor sonde, fix the main lifting cable to the shackle on top of the strain relief mechanism and run the signal cable through the mechanism using the built-in clamps (without tightening them).
  • Page 28 Note: If you are installing a 3TB in a deep borehole, the weight of the sensor will stretch the load bearing cable slightly. Remember to allow for this when raising or lowering the cable in the following steps.
  • Page 29 Güralp 3TB Installing the 3TB in a borehole 14. At approximately 20-meter intervals, fix the signal cable to the load bearing cable using cable clamps (nylon cable ties every five metres may be sufficient for shallow installations). This will ensure that the signal cable does not become kinked or trapped within the borehole.

  • Page 30: Assembling The Winch

    Güralp 3TB Installing the 3TB in a borehole 4.3 Assembling the winch If required, Güralp Systems can provide a winch suitable for installing a borehole sensor. The winch and tripod are supplied as a set of parts which you can assemble on site.
  • Page 31 Güralp 3TB Installing the 3TB in a borehole 3. Erect the tripod above the borehole, and run the yellow retaining tape through the loops. Fasten together the ends of the tape. 4. The lifting cable is supplied with a loop at one end. Run this over one of the pulleys at the top of the tripod, so that the loop hangs down between the legs.
  • Page 32 Güralp 3TB Installing the 3TB in a borehole 6. Extend each of the three legs in turn to the height you require, leaving the leg with the winch attached until last. 7. Take the end of the load-bearing cable without the loop, and screw it to the axle inside the winch using a 4 mm hexagonal key (provided) as shown.
  • Page 33 Güralp 3TB Installing the 3TB in a borehole 8. Attach the handle to the side of the winch opposite the ratchet mechanism, and fasten it in place with a collar, washer and screw, using the larger hexagonal key. 9. Wind the cable onto the winch by rotating the handle. Ensure that the cable builds up neatly across the drum.

  • Page 34: Earthing A Borehole Sensor

    Güralp 3TB Installing the 3TB in a borehole 10. Remove the handle, and screw it onto the metal spool of the ratchet mechanism. 11. Hang the strain relief unit and instrument(s) from the loop at the other end of the cable. You are now ready to lower the assembly into the borehole as described above.

  • Page 35: Installations With Ac Power Supplies

    Güralp 3TB Installing the 3TB in a borehole 4.4.1 Installations with AC power supplies If you are using mains (outlet) power, or some other AC power distribution system, we recommend installing a fully isolating transformer between it and the power supply for the instrument.
  • Page 36 Güralp 3TB Installing the 3TB in a borehole The best local earth point in many installations is the borehole itself. For this to work, the borehole must have a conductive casing and be situated close (<30 m) to the surface installation. In such an installation you need only connect a cable (green wire in the photograph below) from the local ground plate to the borehole casing.

  • Page 37: Installations With Dc Power Supplies

    Güralp 3TB Installing the 3TB in a borehole For boreholes with a metallic casing at the bottom and plastic above, we recommend connecting a cable between the sensor housing and the ground plate so that the lower borehole casing acts as the earthing point.
  • Page 38 Güralp 3TB Installing the 3TB in a borehole However, DC/DC converters contain sensitive electronics, which must be protected thoroughly. We recommend installing a full surge protection unit in addition to the spark gap protector. This protection is installed on the supply side of the isolator, so it must be earthed separately from the borehole installation.

  • Page 39: External Lightning Protection

    Güralp 3TB Installing the 3TB in a borehole 4.4.3 External lightning protection The surface installation building and, if possible, the borehole should both be protected by lightning conductors. These should lead to grounding point well away from the borehole. As a rule of thumb, a lightning mast provides a “zone of protection”...

  • Page 40: Down-Hole Orientation

    Güralp 3TB Installing the 3TB in a borehole output is in the red shaded region, you should not attempt to unlock or centre the sensor masses. Instead, if possible, you should move the instrument within the borehole to a place where it can lie closer to vertical.

  • Page 41: Installing The Scream! Extension

    Güralp 3TB Installing the 3TB in a borehole Once you know the deviation of the borehole components, you can instruct the digitizer to rotate the signals algorithmically. 4.6.1 Installing the Scream! extension The Relative Orientation extension is supplied in the standard Windows distribution of Scream.
  • Page 42 Güralp 3TB Installing the 3TB in a borehole A WaveView window will open displaying your recorded streams: 2. Drag the streams across the window so that the reference stream is at the top, the N stream in the middle, and the E stream at the bottom.
  • Page 43 Güralp 3TB Installing the 3TB in a borehole When you are happy with the selection, release the mouse button, but keep held down. 5. When the context menu appears, release and select Relative Orientation from the menu: Two small windows will appear: a progress window:...
  • Page 44 Güralp 3TB Installing the 3TB in a borehole If you see a different error message, make sure that the streams are in the correct order in the WaveView window. If you still have problems, you may have selected too few data points for it to be confident about the orientation;...
  • Page 45 Güralp 3TB Installing the 3TB in a borehole The lower graph shows the overall amplitude similarity of the rotated signal. This provides an idea of the sign of the coherence (since signals in perfect antiphase have a high coherence as well as those in phase). If there are two peaks in the coherence graph, the correct one is where the amplitude similarity is most positive.
  • Page 46 Güralp 3TB Installing the 3TB in a borehole 9. A new graph will be displayed showing the results: Our sample instrument is thus aligned at –90.61 ± 0.07°. 10. The error given is only a rough estimate. For best results, you should repeat the orientation experiment several times using different data sets.

  • Page 47: Applying Automatic Rotation

    Güralp 3TB Installing the 3TB in a borehole The chosen frequency range can then be entered into the Between X and Y Hz boxes at the top of the Coherence vs Angle window before clicking again; the data will be filtered accordingly before the coherence is recalculated, increasing the accuracy of the result.
  • Page 48 Güralp 3TB Installing the 3TB in a borehole You should see an ok prompt, indicating that the digitizer is ready to receive commands: 2. Type 0 rotation AZIMUTH where rotation is the angle of deviation from true North that you measured earlier, as a whole number of tenths of a degree.
  • Page 49 Güralp 3TB Installing the 3TB in a borehole 3. Reboot the digitizer with the command re-boot. 4. Collect some more data with the transformation active, and carry out another orientation calculation. The data from the down-hole instrument should now have a maximum coherence with the reference sensor at 0 °. Check in particular that the sign of the rotation you have applied is correct.

  • Page 50: Calibrating The 3Tb

    Velocity Output (Differential) : The sensitivity of each component to velocity • at 1 Hz, in volts per m/s. Because the 3TB uses balanced differential outputs, the signal strength as measured between the +ve and –ve lines will be twice the true sensitivity of the instrument.
  • Page 51 Güralp 3TB Calibrating the 3TB This relationship, given in terms of the Laplace variable s , takes the form ( V / x ) ( s ) = G × A × H ( s ) In this equation G is the acceleration output sensitivity (gain constant) of the instrument.

  • Page 52: Frequency Response Curves

    Calibrating the 3TB 5.1.2 Frequency response curves The frequency response of each component of the 3TB is described in the normalised amplitude and phase plots provided. The response is measured at low and high frequencies in two separate experiments. Each plot marks the low- frequency and high-frequency cut-off values (also known as –3 dB or half-power...

  • Page 53: Obtaining Copies Of The Calibration Pack

    5.2 Calibration methods Velocity sensors such as the 3TB 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 54: Calibration With Scream

    Güralp Handheld Control Units provide a switch for activating the CAL ENABLE line. This is most easily done using Scream, as described in the next chapter. Note: Unlike surface 3T instruments, the 3TB has only one calibration enable line for all components.
  • Page 55 Güralp 3TB Calibrating the 3TB 3. Open a Waveview window on the calibration signal and the returned streams by selecting them and double-clicking. The streams should display the calibration signal combined with the sensors' own measurements. If you cannot see the calibration signal, zoom into the Waveview using the scaling icons at the top left of the window or the cursor keys.
  • Page 56 Güralp 3TB Calibrating the 3TB Most data can be found on the calibration sheet for your sensor. Under Instrument response , you should fill in the sensor response code for your sensor, according to the table below. Instrument Type should be set to the model number of the sensor.

  • Page 57: Sensor Response Codes For 3Tb Instruments

    R is the magnitude of the calibration resistor and K is the feedback coil constant. R and K are both given on the calibration sheet supplied with the 3TB. The calibration resistor is placed in series with the transducer. Depending on the calibration signal source, and the sensitivity of your recording equipment, you may need to increase R by adding further resistors to the circuit.
  • Page 58 Güralp 3TB Calibrating the 3TB 3. Repeat this measurement for several tilt angles. 4. For the vertical sensor, the input acceleration is given by a  =  g  sin  φ , whilst for the horizontal sensor, it is a  =  g  ( 1 – cos  φ  ).

  • Page 59: Inside The 3Tb

    These adjustments are made by small DC motors controlled remotely. See section 4 on page 21, “Installing the 3TB in a borehole” for detailed instructions on how to set up your 3TB installation. MAN-BHO-0001...

  • Page 60: The Control System

    The 3TB also receives control signals, which are used to clamp and un- clamp the masses, and to run the motors which level and centre the instrument once in position.

  • Page 61: Lock

    Hand-held Control Unit or digitizer. If you send control signals to the 3TB manually, you must ensure that the lines are allowed to float high after sending the signal, or the equipment may be damaged. A “biased-OFF” type switch can be used for this purpose.

  • Page 62: Unlock

    Güralp 3TB Inside the 3TB 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 63 Güralp 3TB Inside the 3TB Again, you can use the BUSY LED to monitor the progress of unlocking. 1. The instrument checks to see whether the vertical mass is locked, and unlocks it if necessary. 2. 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 64: Centre

    Güralp 3TB Inside the 3TB 6.2.3 CENTRE This command re-centres the masses. If the masses are clamped, or if the sensor mass positions do not exceed ± 1.2 V, the CENTRE command does nothing. Otherwise, it attempts to zero the output of the vertical, N/S and E/W sensors in sequence by exerting small extra forces on the boom.

  • Page 65: The Feedback System

    Force feedback seismometers of this type rely on the assumption that the force transducer produces a field of constant strength. The magnetic circuit and magnet/pole assembly in the 3TB are designed so that the field strength from the feedback transducer is constant over large deflections and current levels. Tests have...

  • Page 66: Hybrid Feedback

    There are two types of feedback system which can be used in a 3TB instrument, known as hybrid and conventional-response feedback. 6.3.1 Hybrid feedback The hybrid feedback circuit contains a single capacitor in parallel with a resistor, resulting in a single dominant pole at 0.033 Hz (30 s).

  • Page 67: Conventional-Response Feedback

    Güralp 3TB Inside the 3TB 6.3.2 Conventional-response feedback The conventional-response feedback system has an additional parallel feedback circuit, consisting of a non-inverting integrator in series with a resistor. This arrangement results in two poles at specified frequencies. The velocity response of a conventional-response system is defined by a transfer function identical to that of a conventional long-period sensor with a damping constant ζ...
  • Page 68 Güralp 3TB Inside the 3TB MAN-BHO-0001 Issue G - November 2019...

  • Page 69: Connector Pin-Outs

    Güralp 3TB Connector pin-outs 7 Connector pin-outs 7.1 Break-out Box – Power connector These are standard 10-pin “military-specification” sockets, conforming to MIL-DTL-26482 (formerly MIL-C-26482). A typical part-number is 02E-12-10S although the initial “02E” varies with manufacturer. Suitable mating connectors have part-numbers like ***-12-10P and are available from Amphenol, ITT Cannon and other manufacturers.

  • Page 70: Break-Out Box - Recorder And Control Connectors

    Güralp 3TB Connector pin-outs 7.2 Break-out Box – Recorder and Control connectors This is a standard 26-pin “military-specification” plug, conforming to MIL-DTL-26482 (formerly MIL-C-26482). A typical part-number is 02E-16-26P although the initial “02E” varies with manufacturer. Suitable mating connectors have part-numbers like ***-16-26S and are available from Amphenol, ITT Cannon and other manufacturers.

  • Page 71: Break-Out Box - Sensor Connector

    Güralp 3TB Connector pin-outs 7.3 Break-out Box – Sensor connector This is a standard 26-pin “military-specification” plug, conforming to MIL-DTL-26482 (formerly MIL-C-26482). A typical part-number is 02E-16-26P although the initial “02E” varies with manufacturer. Suitable mating connectors have part-numbers like ***-16-26S and are available from Amphenol, ITT Cannon and other manufacturers.

  • Page 72: Instrument - Sensor Connector

    Güralp 3TB Connector pin-outs 7.4 Instrument - Sensor Connector This is a custom 32-pin plug with pin spacing and layout conforming to MIL-DTL-26482 (formerly MIL-C-26482). The GSL part number is ELM-32P- 18FX+MEC-GEN-1002-32W. Pin Function Pin Function Hole-lock motor Inclinometer output - Y...

  • Page 73: Specifications

    Güralp 3TB Specifications 8 Specifications Hybrid sensors Velocity output bandwidth 0.1 – 50 Hz High pass filter output flat to   0.01 Hz – spec* acceleration   High pass filter output flat to velocity spec – 50 Hz*   Mass position output DC –...
  • Page 74 Güralp 3TB Specifications * 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. ** Sensors are available with a range of sensitivities between 2 × 750 and 2 × 10,000 V/ms † Because centring, locking, and unlocking consume varying amounts of power, it is recommended that you use a power supply capable of delivering 1 A at 12 V.

  • Page 75: Revision History

    Güralp 3TB Revision history 9 Revision history 2019-11-13 Amended diameter. Replaced orientation chapter. Updated images 2018-03-12 Removed "direct" from pin-outs 2017-11-06 Added baffle details 2016-01-02 Face-lift with no significant content changes 2013-04-17 Added surge arrestor/stress relief details 2006-11-15 Updated Scream! and SOH; added revision history...

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