Guralp-systems CMG-3TB Manual de usuario

CMG-3TBOperator’s guidePart MAN-BHO-0001Designed and manufactured byGüralp Systems Limited3 Midas House, Calleva ParkAldermaston RG7 8EAEnglandProprie

CMG-3TBheld parallel to the axis of the borehole and prevented from twisting or slipping under the influence of ground vibrations.10 Issue C

Operator's guide2 Assembling the instrument2.1 Unpacking and packingThe 3TB seismometer is delivered in a single transportation case, with the

CMG-3TBinstallation of the device, you should contact Güralp Systems for assistance.• Do not bump or jolt any part of the sensor whe

Operator's guide1. Ensure that the “O”-ring seals on the hole lock and sensor sections are clean and well greased.2. Stand th

CMG-3TBconnectors. Ensure that each is connected to its correct counterpart.hole lock unit at an angle above the horizontal sensor and

Operator's guide6. Push the hole lock unit into the horizontal sensor housing, twisting to align the holes.7. Fit twelve M3×8 c

CMG-3TB11.Push the vertical sensor housing into the hole lock–actuator section, twisting to align the holes.12.Fit twelve M3×8 screws int

Operator's guidescratching the other components.2.5 Control unitsThe 3TB is operated from the surface through various control units. All the 3TB&

CMG-3TBdigitizer. In systems using downhole digitizers, this is replaced by a 10-way mil-spec serial connector for attaching to a Data Communications

Operator's guideneed to move the instrument.To unlock the instrument, hold down the ENABLE and UNLOCK buttons (or the UNLOCK swi

CMG-3TBTable of Contents1 Introduction...

CMG-3TBConnectionsThe HCU provides• two identical 26-pin connectors for attaching to the HCU or RECORDER connectors of the breakout box,

Operator's guide• You can set the range of the meter with the RANGE switch. When switched to 10 V, the meter ranges from –10 to +10 V (as ma

CMG-3TBTo measure the attitude of a 3TB instrument:1. Connect the inclinometer monitor unit to the CONTROL connector of the breakout box.

Operator's guideCaution: The hole lock may be using high-voltage mains (outlet) power.1. Connect the hole lock control unit to t

CMG-3TBunit, there will be an additional dial compared to the unit pictured; turn this until the built-in ammeter reads around 0.1

Operator's guide0 V.• To retract the jaw, reverse the polarity so that the Hole Lock Motor Return pin is at +12 V and the Hole Lock Motor pin is

CMG-3TB3 Installing the 3TB in a boreholeBefore installing any instrument in a borehole, you should prepare the installation site.• Clean the area aro

Operator's guide 2. If applicable, you should test the hole lock mechanism before installing the sensor. For safety reasons, the

CMG-3TB4. Attach the lifting loop to the sensor using four M5×16 screws (provided).5. Join the loop to the bottom of the strain relief mechanism using

Operator's guide 7. Fix the signal cable to the main lifting cable about 1 m above the strain relief mechanism using a metal clamp (a n

Operator's guideInstalling the Scream! extension... 47Installing the referenc

CMG-3TBfails to register ground movements, contact Güralp Systems.15.Lock the sensor masses once more, tension the load bearing cable and retr

Operator's guide3.2 Installing a sensor using sand backfillDry sand backfill is a convenient and effective way of installing a bo

CMG-3TBProcedureTo install a sensor at the bottom of a borehole of known depth using sand backfilling:1. Measure or calculate the physical volume of t

Operator's guide5. Attach the lifting loop to the sensor using four M5×16 screws (provided).6. Join the loop to the bottom of the strain relief m

CMG-3TB 8. Fix the signal cable to the main lifting cable about 1 m above the strain relief mechanism using a metal clamp (a nylon cable tie

Operator's guide14.Whilst monitoring the depth of the sensor, carefully approach the sand layer at the bottom of the borehole. The lifting cable

CMG-3TB3.3 Assembling the winchIf required, Güralp Systems can provide a winch suitable for installing a borehole sensor. The winch and tripod are sup

Operator's guide3. Erect the tripod above the borehole, and run the yellow retaining tape through the loops. Fasten together th

CMG-3TBfinishing at the leg with the winch attached.7. Take the end of the load-bearing cable without the loop, and screw it to the axle inside the wi

Operator's guide9. Wind the cable onto the winch by rotating the handle. Ensure that the cable builds up neatly across the drum.

CMG-3TB1 IntroductionThe CMG-3TB is a three-axis seismometer consisting of three sensors stacked vertically in a sealed borehole sonde, designed for u

CMG-3TB11.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 as

Operator's guidewhich is connected to a local ground plate. All earth lines for equipment in the installation, such as the

CMG-3TBAn earth strap can be used to ensure a good connection.If the lower borehole is filled with salt water, the instrument will be adequately groun

Operator's guideThe best option is often to attach the sensor housing to an earth line brought out to the surface and attached to a metal stake d

CMG-3TBFor boreholes with a metallic casing at the bottom and plastic above, we recommend connecting a cable between the sensor housing and the ground

Operator's guideAs with AC installations, if the borehole is more than around 30 m from the surface enclosure, you will need to provide a second

CMG-3TB3.5 Levelling and centringOnce it is installed, you should level and centre the instrument ready for use. This can be done using the various su

Operator's guide3.6 Downhole orientationOnce the sensor is installed inside the borehole, you will need to measure its orientati

CMG-3TBeach one to settle. This process takes at least 12 hours.Measuring the orientation1. Run Scream!. Open the File – Setup window, and selec

Operator's guideThe N and E streams are the “North/South” and “East/West” components of the downhole instrument. The X stream is the North

Operator's guide1.1 System configurationThe CMG-3 series of seismic instruments share a number of features:• a modular sensor sonde, which can be

CMG-3TBWhen you are happy with the selection, release the mouse button, but keep SHIFT held down.11.When the menu appears, release t

Operator's guideThe two-stage algorithm rotates the N/S and E/W components of the sensor being tested in small steps.It measures first the

CMG-3TBthe signal, i.e. the time series that a sensor in perfect N/S orientation would have produced:14.You can perform more accur

Operator's guideOur sample instrument is thus aligned at –90.35 ± 0.07 °.16.The error given is only a rough estimate.You should repeat the

CMG-3TBYou should see an ok prompt, indicating that the digitizer is ready to receive commands.2. Type0 rotation AZIMUTH where rotation is the angle

Operator's guide4 Calibrating the 3TB4.1 The calibration packAll Güralp sensors are fully calibrated before they leave the factory. Both absolute

CMG-3TBPoles and zeroesMost users of seismometers find it convenient to consider the sensor as a “black box”, which produces an output signal V from

Operator's guideFrequency response curvesThe frequency response of each component of the 3TB is described in the normalised amplitude and phase p

CMG-3TB4.2 Calibration methodsVelocity sensors such as the 3TB are not sensitive to constant DC levels, either as a result of their de

Operator's guideDepending on the digitizer type, sine-wave, step and broadband noise signal generators may be available. In this section, broadba

CMG-3TBThe CMG-3V sensor is identical to the vertical-component module of the 3TB instrument, allowing you to build mixed arrays of 3V and 3TB sensors

CMG-3TBsensors' own measurements. If you cannot see the calibration signal, zoom into the Waveview using the scaling icons at the top left of the

Operator's guideMost data can be found on the calibration sheet for your sensor. Under Instrument response, you should fill in the

CMG-3TBThe bbnoisecal script automatically performs appropriate averaging to reduce the effects of aliasing and cultural noise.Sensor response

Operator's guideDepending on the calibration signal source, and the sensitivity of your recording equipment, you may need to increase R by addi

CMG-3TB5 Inside the 3TB5.1 The sensorsThe horizontal and vertical sensors are similar in design. The inertial mass in both cases consists of

Operator's guideThe signal voltages output by the 3TB are proportional to ground velocity, and are transmitted from

CMG-3TB5.2 The control systemThe internal operations of the 3TB are supervised by a control microprocessor, which drives the

Operator's guideIn 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 b

CMG-3TBAgain, you can use the BUSY LED to monitor the progress of unlocking.1. The instrument checks to see whether th

Operator's guideCENTRE This command re-centres the masses. If the masses are clamped, or if the sensor mass positions do not exceed

Operator's guideA digital borehole installation can be provided with RS232, RS422 or fibre-optic links to the surface, depending on

CMG-3TBAfter the sensor unlocks the masses, the first round of centring has to move the N/S and E/W components all the way from their end stops, whils

Operator's guideIn a feedback seismometer with a displacement transducer, it is essential to monitor the acceleration output. T

CMG-3TBConventional-response feedbackThe conventional-response feedback system has an additional parallel feedback circuit, consisting of a non-invert

Operator's guide November 2006 73

CMG-3TB6 Connector pinoutsThis table combines the pinouts for all connectors on the borehole sensor and breakout box. Control signals are normally ac

Operator's guideV U U CentreX V V DirectZ W W UnlockY X X Lockb Acc/Vel mode switch*e N N Signal groundf Y Y E Control signal grou

CMG-3TB7 SpecificationsHybrid sensors Velocity output bandwidth 0.1 – 50 Hz High pass filter output flat to acceleration0.01 Hz – spec* High pass filt

Operator's guide*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.**Sens

CMG-3TB8 Revision history2006-11-15 C Updated Scream! and SOH; added revision history2005-05-12 B Original document78 Issue C

CMG-3TBborehole, providing two line contacts;• only the tips of the skids come into contact with the borehole, providing three point contacts;• a sing

Operator's guide Studs have the advantage of being smaller than skids, but the contact points are very close to each other. You should evalua