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Introduction

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Introduction

The Güralp 40T is a lightweight seismometer consisting of three sensors in a sealed,
stainless steel case, which can measure the north/south, east/west and vertical
components of ground motion simultaneously.

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Issue F - June 2019

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Summary of Contents for 40T

Page 1: ...Güralp 40T Operator s Guide Document No MAN 040 0001 Issue F June 2019 Designed and manufactured by Güralp Systems Limited 3 Midas House Calleva Park Aldermaston RG7 8EA England ...

Page 2: ...Calibration 9 3 2 2 3 Control commands 9 3 2 2 4 Banana plugs 9 3 3 Levelling the instrument 10 3 4 Zeroing the instrument 10 3 4 1 Adjusting the mass position offsets manually 11 3 4 2 Adjusting the mass position offsets with an HCU 12 3 4 3 Zeroing a 40TD digital instrument 13 3 4 4 Digital nulling operation 16 4 Installing the 40T 17 4 1 Installation notes 17 4 2 Installing in vaults 18 4 2 1 C...

Page 3: ...bration pack 27 5 2 Calibration methods 28 5 3 Calibration with Scream 28 5 3 1 Sensor response codes 32 5 4 Calibration with a hand held control unit 32 6 Connector pin outs 34 6 1 Output port and breakout box RECORDER connector 34 6 2 Output port and breakout box RECORDER connector high gain option 36 6 3 Breakout box power connector 37 7 Specifications 38 8 Revision history 40 MAN 040 0001 3 Is...

Page 4: ...s liable 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 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...

Page 5: ...n The Güralp 40T is a lightweight seismometer consisting of three sensors in a sealed stainless steel case which can measure the north south east west and vertical components of ground motion simultaneously MAN 040 0001 5 Issue F June 2019 ...

Page 6: ...libration levels and the transfer function in poles zeros notation 2 1 Response options The standard frequency response for a 40T is flat to velocity from 60 seconds 0 017 Hz to 100 Hertz Standard alternative frequency response options are flat to velocity from 30 seconds 0 03 Hz to 100 Hertz flat to velocity from 1 second 1 Hz to 100 Hertz Other frequency response options have been manufactured i...

Page 7: ...ch provides separate connectors for signal and power An optional hand held control unit provides individual connectors for every output signal These are described in the following sections 3 2 1 The breakout box If you are using a Güralp breakout box it should be attached to the sensor through its SENSOR connector Connectors are also provided at the CONTROL and RECORDER outputs for attaching to a ...

Page 8: ...isplaying the output velocity and mass position i e acceleration on an analogue meter 3 2 2 1 Signal meter The upper section of the HCU contains a simple voltmeter for monitoring various signals from the instrument To monitor the low gain outputs switch the dial to V N S or E W LOW VEL according to the component you want to monitor To monitor the high gain outputs on a 40T with that option switch ...

Page 9: ...AL inputs and setting the adjacent switch to ON The sensor s response can now be monitored or recorded and calibration calculations carried out See Chapter 5 on page 25 for full details 3 2 2 3 Control commands If you have ordered a 40T with the remote null facility you can zero its mass position offsets from the HCU 1 Select the component you want to centre from the CENTRING SELECT dial 2 Switch ...

Page 10: ...T you should check that the mass positions are not significantly offset from zero The 40T must be perfectly level for this to be effective The mass position offsets can be affected by any tilt to the instrument as well as rough handling during transportation The normal range of the mass positions is 10 V you should zero the instrument if any mass reads more than around 3 5 V 35 of full scale when ...

Page 11: ...ross the Acc Vel and Signal Ground pins of the input If you are using a DM24 you can do this by sending a CENTRE command If you are using a Hand held Control Unit you should select 1 SEC VEL from the Velocity Select switch 2 Measure the vertical mass position output with a 10 V voltmeter see Chapter 6 on page 34 for pin out details or by selecting MASS POS V from a Hand held Control Unit s Display...

Page 12: ...tring option which allows you to adjust the internal potentiometers by applying voltages across control lines to the sensor 1 Bring the instrument into 1 second response mode by selecting 1 SEC VEL from the Velocity Select switch 2 Measure the vertical mass position output by selecting MASS POS V from the Hand held Control Unit s Display Select knob 3 Set the Centring Select knob to V 4 Press the ...

Page 13: ...sor itself You can monitor the mass position outputs of the sensor using a Hand held Control Unit and an adapter cable available from Güralp Systems To change the offsets of a 40TD without digital centring 1 Check the bubble level on the lid of the instrument to ensure it is not tilted If necessary re level the instrument by adjusting its feet Take care not to disturb the instrument during the sub...

Page 14: ...are that the vent cap does not fly off when released causing injury 3 Using a hexagonal wrench remove the screws holding the digitiser module onto the sensor 4 Place a flat head screwdriver in the notches provided and holding the bottom part of the instrument steady twist the screwdriver to lever off the upper digitiser module MAN 040 0001 14 Issue F June 2019 ...

Page 15: ...hree holes in the topmost electronics board which provide access to the offset potentiometers Insert a screwdriver through the appropriate hole and engage the potentiometer for the vertical component 9 Adjust the potentiometer until the mass position output reads close to zero 10 Repeat steps 4 6 for the north south and east west components Alternatively you can adjust the mass positions and monit...

Page 16: ...itions of all three axes simultaneously Zeroing can be further triggered via the centre control line on pin U On instruments without the digital nulling option grounding pin U to pin Y puts the instrument into one second mode Automatic zeroing takes approximately forty five seconds to complete after which the sensor reverts to long period operation and the nulling module enters a low power sleep m...

Page 17: ...rue ground motion ideally beyond the range of the instrument This is done by standing the sensor on bedrock where possible or at least deep in well compacted subsoil clearing the floor of the hole of all loose material and using as little extra mass as possible in preparing the chamber In temporary installations environmental factors are also important The sensor needs to be well protected against...

Page 18: ... 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 set up has a number of advantages It is installed below ground Most man made noise tends to...

Page 19: ...ystems 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 4 2 2 Temperature stability The 40T 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 i...

Page 20: ...ipment 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 South...

Page 21: ...nt directly on the bedrock and go to step 7 3 On soft bedrock or subsoil you should install a pier as depicted below 4 Pour a layer of loose fine sand into the pit to cover the base The type of sand used for children s sand pits is ideal since the grains are clean dry and within a small size range On top of the sand place a smooth flat granite plinth around 20 cm across and shift it to compact the...

Page 22: ...e shielded from air currents and temperature fluctuations This is best done by covering it with a thermal shield An open sided box of 5 cm expanded polystyrene slabs is recommended If using a seismic plinth on sand from steps 3 4 or 5 ensure that the box is firmly placed in the sand without touching the plinth at any point In other installations tape the box down to the surface to exclude draughts...

Page 23: ...ommend the use of fine dry sand right contained in a box if necessary which can also insulate the instrument against convection currents and temperature changes Sand has the further advantage of being very easy to install requiring no preparation Finally many pit installations have a large space around the seismometer covered with a wooden roof Large air filled cavities are susceptible to currents...

Page 24: ...Güralp 40T Installing the 40T MAN 040 0001 24 Issue F June 2019 ...

Page 25: ...es will be twice the true sensitivity of the instrument To remind you of this the sensitivities are given as 2 single ended sensitivity in each case Mass Position Output The sensitivity of the mass position outputs to acceleration in Volts per ms These outputs are single ended and referenced to signal ground Feedback Coil Constant A constant describing the characteristics of the feedback system Yo...

Page 26: ... j 1 n s Pj In this equation Zi are the roots of the numerator polynomial giving the zeros of the transfer function and Pj are the roots of the denominator polynomial giving the poles of the transfer function In the calibration pack G is the sensitivity given for each component on the first page whilst the roots Zi and Pj together with the normalising factor A are given in the Poles and Zeros tabl...

Page 27: ... s response 5 1 3 Obtaining copies of the calibration pack Our servers keep copies of all calibration data that we send out In the event that the calibration information becomes separated from the instrument you can obtain all the information using our free e mail service Simply e mail caldoc guralp com with the serial number of the instrument in the subject line e g The server will reply with the...

Page 28: ...o the calibration coil gives the response of the whole system which can be measured using a spectrum analyser You can perform calibration either using a Güralp DM24 digitiser which can generate step and sinusoidal calibration signals or by feeding your own signals into the instrument through a hand held control unit Before you can calibrate the instrument its calibration relays need to be activate...

Page 29: ...nding Cn n 0 7 or MB should appear in Scream s main window containing the returned calibration signal 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 ...

Page 30: ...nd select Scale You can then type in a suitable scale factor for that trace 6 Pause the WaveView window by clicking on the button 7 Hold down and drag across the window to select the calibration signal and the returning component s Release the mouse button keeping held down A menu will pop up Choose Broadband Noise Calibration 8 The script will ask you to fill in sensor calibration parameters for ...

Page 31: ... g GURALP DEMO It is always 6 characters the system identifier followed by a dash then 4 characters the serial number For example 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 9 Click The script will return with a graph showing the response of the sensor in terms of amplitude...

Page 32: ...nse CMG 40_1S_100HZ V 40T 1 or 6T 1 2 s 100 Hz response CMG 40_2S_100HZ V 40T 1 or 6T 1 10 s 100 Hz response CMG 40_10S_100HZ V 40 20 s 50 Hz response CMG 40_20S_50HZ V 40 30 s 50 Hz response CMG 40_30S_50HZ V 40 60 s 50 Hz response CMG 40_60S_50HZ V 5 4 Calibration with a hand held control unit If you prefer you can inject your own calibration signals into the system through a hand held control u...

Page 33: ...libration signal f is the signal frequency 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 40T 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 res...

Page 34: ...unction Pin Function A Velocity ve vertical ch P Calibration signal all channels B Velocity ve vertical ch R Calibration enable all channels C Velocity ve N S ch S Not connected D Velocity ve N S ch T Not connected E Velocity ve E W ch U One second mode F Velocity ve E W ch V N S centring motor G Mass position vertical ch W E W centring motor H Not connected X Vertical centring motor J Mass positi...

Page 35: ...ity outputs and run calibrations Pressing ENABLE and CENTRE on a Güralp 3ESP hand held control unit activates pin U and switches the 40T into one second mode for as long as the buttons are held down You must do this before you can monitor mass position outputs e g for offset zeroing Note 40T units with the optional additional high gain outputs cannot be used with a Güralp 3ESP breakout box The pin...

Page 36: ...rers Pin Function Pin Function A Velocity ve vertical ch P Calibration signal all ch B Velocity ve vertical ch R Calibration enable all ch C Velocity ve N S ch S HGV ve vertical channel D Velocity ve N S ch T HGV ve vertical channel E Velocity ve E W ch U Acc Vel or Centre see P16 F Velocity ve E W ch V N S centring motor G Mass position vertical ch W E W centring motor H HGV ve E W channel X Vert...

Page 37: ...facturer Suitable mating connectors have part numbers like 12 10S and are available from Amphenol ITT Cannon and other manufacturers Pin Function A Power 0 V B 12 V DC supply C Not connected D Not connected E Not connected F Not connected G Not connected H 12 V DC supply 3 way power option J Not connected K Not connected Wiring details for the compatible socket 12 10S as seen from the cable end MA...

Page 38: ... s Contact Güralp to discuss alternative high sensitvity high gain options Peak full scale output voltage Differential 20 V 40 V peak to peak Single ended e g mass positions 10 V 20 V peak to peak Self noise below NLNM New Low Noise Model Peterson 1993 USGS 7 s 0 15 Hz to 4 Hz Independently tested value see Tasic Runovc 2012 Journal of Seismology Sensor dynamic range standard sensitivity 148 dB 1 ...

Page 39: ...erature range 20 to 75 C Operating humidity range 0 100 relative humidity Enclosure ingress protection IP68 protection against effects of prolonged immersion at 3 m depth for 72 hours Posthole option For deeper long term immersion the optional 100 bar 10 MPa waterproof connector is recommended Enclosure material Stainless steel case O ring seals throughout Diameter 168 mm Height With handle 203 mm...

Page 40: ... E Added Levelling section 29 June 2016 D Added safety warning about pressure relief screw Enhanced specifications Minor edits elsewhere 3 May 2016 C Face lift with no significant content changes 22 Jul 2009 B Added digital nulling option improved connector documentation added revision history 12 Jan 2006 A New document MAN 040 0001 40 Issue F June 2019 ...

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