BROADBAND SEISMOMETER TESTING

BROADBAND SEISMOMETER TESTING 

Introductory remarks

1. The broadband seismometers and related seismic equipment are products of Güralp Systems Ltd. (GSL), who integrated the instruments into spherical titanium pressure cases, an MBARI design licensed to NEPTUNE Canada.   Three such systems will be deployed in 2009.

2. It is desired to avoid duplication of effort & required knowledge between PGC and MTC. 
   

General Information

1. Each NEPTUNE Canada broadband seismometer system includes a spherical titanium pressure case housing the seismic detectors, which will be surficially buried in a caisson set into the seafloor sediment.  A small frame will be located 20m away, where underwater mateable connectors and ancillary equipment will be located.  The spheres (with contents) and cable/connector assemblies are completely interchangeable.   Each system comprises...

1. Titanium sphere containing ... 
   

1. CMG-1T broadband seismometer 
   
2. CMG-5T strong motion accelerometer
3. CMG-DM24 digitizer
4. CMG-EAM embedded acquisition module
5. high stability real time clock synchronized to NTP
6. Power controller
7. Tilt platform
8. Magnetometer compass for determining orientation of sphere
9. Temperature sensor for electronics

2. Small frame 20m from sphere containing ... 
   

1. Nortek Aquadopp current meter* 
   
2. SCRIPPS differential pressure gauge*
3. Battery case*
1. 6kW-hr lithium battery
2. mercury tilt switch
4. Three underwater mateable connectors†

      * not at Barkley       † one at Barkley

2. The 6 kW-hr battery provides ~30 days of operation in the event cable power fails.  While on cable power, this backup feature can be disabled to avoid using the battery during anticipated outages, especially during the start-up period.  

3. Each titanium sphere comprises two hemispheric castings, individually identified by a casting ID number (e.g. 1P2) and a Furnace Pour number (e.g. 559).  These castings were randomly paired and assembled into spheres as indicated below. 
   

                           top         bottom

1  P2/558 – 2P3/559

2  3P5/560 – 2P4/559

3  1P1/558 – 3P6/560 


As paired, the spheres were pressure tested at DRDC Atlantic to DSV Alvin specs for implodable volumes carried by manned submersible.  The maximum test pressure was 6000 psi. 

4. Test cables for Broadband systems (MIN-M-25-CCP mates to top of sphere)
2. Güralp wired MINM for bench tests
3. Barkley deployment cable (use to check power and Ethernet on any BB system, should

be delivered first)

4. MIN-M-25-CCP available

5. Broadband deployment cables (molded)   (See BB Seismometer Layout, appended to this doc)  
   
1. Standard cable assembly  (3 identical assemblies)
1. MIN-M-25-CCP (on sphere) to
1. ROV ODI-12 to NEPTUNE Canada
2. ROV ODI-12 to instrument gather to
1. Fixed ODI-12 (instrument gather) to
1. Aquadopp via LPMIL-8-MP
2. Differential pressure gauge via RMG-4-FS
3. Fixed ODI-4 (battery) to
1. ROV ODI-4 to
1. battery via XSEE-2-CCP

2. Barkley special: (NC power & Ethernet only) 
   
1. MIN-M-25-CCP (on sphere) to
1. ROV ODI-12 to NEPTUNE Canada

6. CMG-EAM IP addresses to be pre-programmed by GSL or by Martin Hofmann 
   

    Barkley      ODP 889      ODP 1027

192.168.101.191  192.168.101.193 192.168.101.194

10.136.52.132  10.136.164.130  10.136.68.130

10.156.52.129  10.156.164.130   10.156.68.129 

VLAN 101 for monitoring & control

VLAN 136 for Aquadopp

VLAN 156 for Antelope/SEED 
 
 


Güralp tests (presumed) 


1. Range of tilts demonstrated and documented
2. Environmental requirements
1. chamber at 1.8°C for extended period of time
3. Side by side noise levels
4. Test entire OBS sensor in vault for extended period of time
5. Cold start -10°C
6. Transportation simulation tests
7. TBD
 
 
 


MTC Testing 


1. Goals
1. Primary: ensure network is not adversely affected or its functionality limited.
2. Secondary:  ensure serviceability and functionality, verify data format.
3. Tertiary:  test deployment cables if available
2. Joint approach to testing between MTC and PGC 
   
1. Avoid duplication of effort and knowledge between PGC and MTC.
2. Network related issues and basic operation to be tested at MTC (with RDM present).
3. In-depth operational tests to be done in PGC vault.
3. Special requirements 
   
1. Lab supply 48VDC
2. current meter (in-line preferred), or in supply
3. Microphone/loudspeaker  (to hear motor noises)  RDM
4. PC (Windows or Linux) with Web browser and
1. Güralp SCREAM! Software (optional)
5. Plate on which to mount sphere for tilt tests to 20°
6. Two 12V car batteries to help assessing supply induced noise (late night at MTC)
7. Documentation (See 2.a above)
1. Güralp recommended procedure for initial checkout or acceptance (missing)
2. CMG-1T manual  (missing)
3. CMG-5T manual
4. CMG-DM24 manual
5. CMG-EAM manual
6. SCREAM! Manual
7. Güralp How-to guides
1. Troubleshooting DCM installations
2. Troubleshooting DM24 mk3 digitizers
8. Broadband Seismometer Layout, Mar 3, 2009, (RDM) appended
9. Broadband external cabling wiring diagram, April 9, 2009, (RDM) appended
8. Instruments 
   
1. Sphere
2. Nortek Aquadopp (RS-232)
3. SCRIPPS DPG
4. Test cables
5. Deployment cables
1. sphere set (MINM+4)
2. battery set (XSEE)
3. instrument gather
4. Initial Bench Deployment
1. Place titanium sphere on floor using 3 points (bolts in foot? Ceramic spacers?)
2. Ensure seismometer and test cable are secure.
3. Attach microphone and speaker
4. Apply 48VDC power
5. Measure inrush current (expect 400mA)
6. Listen for motor noise
7. Measure steady state current (expect <100 mA) (masses clamped)
8. Confirm web browser communication
1. EAM
2. DM24
3. Clock
1. set clock with reference time
9. EAM setup 
   
1. Program IP addresses if not already programmed
2. Rename channels on Seed name mappings page
1. Network code= NV
2. Station codes: 
1. Barkley Canyon  NCBC
2. ODP 1027  NC27
3. ODP 889  NC89
4. Endeavour  KEBB
3. Channel names      Z         N         E
1. Broadband (BB)  HHZ  HHN HHE
2. Filtered BB  MHZ  MHN  MHE
3. Strong motion (SMA) HNZ  HNN HNE
4. Filtered SMA  MNZ   MNN   MNE
5. Mass Positions  MMZ MMN  MME
6. DPG   MDD
7. temperature  MK1
10. Check magnetometer 
    
1. How powered?
2. Read  heading and compare with
1. External magnetic compass (YYJ variation = 17° 34’ East)
2. Building drawings (MTC)
3. GPS line
3. Attempt to confirm accuracy of 0.2°
11. View accelerometer outputs Z, N, E 
    
12. Check basic operation of levelling system 
    
1. Send and confirm level command, note time
2. Note current drawn
3. Listen for motor noises
4. Watch accelerometer signals Z, N, E
5. Confirm automatic stop, note time
6. Confirm level (using accelerometer outputs)
13. Check levelling system range and speed of operation 
    
1. Turn off 48VDC power
2. Tilt sphere through range of angles (to 15°) and confirm operation
3. When centred at maximum tilt, change tilt direction 180°, measure time to level
14. When levelled, view Z mass position output of seismometer 
    
15. Send command to unlock Z mass, note time 
    
1. Check current
2. Listen for motor noise
3. Watch Z mass position signal
4. Confirm mass is centred, note time
16. Confirm Z velocity output stabilizes 
    
17. Confirm Z velocity data
18. Confirm low pass filtered velocity data
19. Repeat above from “o” for N and E masses
20. Confirm Z, N, E acceleration data  
    
21. Confirm Z, N, E low pass filtered acceleration data
22. Confirm internal temperature data
23. Remove power
24. DO NOT DISTURB SPHERE, proceed to step 5
5. Interrupted operation inrush (do this with configuration of 4v above)   
   
1. Apply 48VDC power, listen for motor noise
2. Measure inrush current
1. Repeat power off/on for consistency, listening for motor)
2. limited to 400 mA?
3. Remove power 
   
1. Connect NORTEK current meter
2. Connect DPG
4. Apply 48VDC power 
   
5. Measure inrush current
6. Repeat if necessary, listen for motor noise
7. Confirm Nortek is alive and communicating
8. Confirm DPG data is present
9. Send command to shut down Nortek
1. record current after shutdown command
2. Confirm no Nortek communication
10. Send command to shut down DPG
1. record current after shutdown command
2. confirm no DPG signal
11. Send command to power up Nortek
1. Confirm operating
12. Send command to power up DPG
1. Confirm operating
6. Backup battery system test (do not prolong operation on deployable battery) 
   
1. Connect battery or power supply set to 14.4VDC
2. If real battery pack check operation of mercury switch & verify label on case
3. Verify voltage at battery output
4. Confirm operation of battery backup enable/disable command
5. Kill cable
1. Nortek and DPG off?
2. steady state current consistent with 4.63W power?
3. system operating okay?
6. Re-power cable and measure inrush from cable
7. JB supply noise (must be done during seismically quiet time of day) 
   
1. Use JB supply to operate system
2. Connect 24v battery to battery input
3. Collect data for 1 hour
4. Kill power 
   
5. Confirm operating normally on battery power
6. Collect data for 1 hour
7. Restore JB power 
   
8. Collect data for 1 hour
9. Compare noise spectra of above three runs

 

 

8. Communications
1. TEF
1. Follow MTC test plan
2. NTP timing operation (where is receiver?)
1. Incorrectly set clock
1. Watch recover to NTP
2. Nortek (RS-232 version) 
   
1. Check as per DMAS stand alones
2. IP issues in sphere? (Martin Hofmann)
9. Isolation (seawater dunk) test (objective?) 
   
1. Spheres with Barkley cable
1. Electrical leakage?
2. Water leak into case (how know?)
3. cable
2. Spheres with full cable set 
   
1. Electrical leakage?
2. Water leak (how know?)
1. Sphere
2. Nortek
3. DPG
4. Battery
5. cables
10. On-line data storage (Nathan emails for details) 
    
 


NEPTUNE Canada Instrument Requirements

1. Pressure testing of case not required
2. Seals
1. Quantity
2. Lubricant
3. Pressure vessel closing, see §4.10.3 Pressure Vessel Closing
4. Cable moulding standards, see §4.11 Test Mouldings
5. All connectors to be protected
 


 PGC testing (seismic vault)

1. Goals
1. Confirm polarity and sensitivity to seismic signals.
2. Find shipping damage, however subtle.
2. Documentation 
   
1. Everything suggested for MTC testing plus the following
2. Guralp How-to guides
1. Calibration with a broadband noise source
2. Calibration with a square wave (step) signal
3. Calibration with a sine wave signal
4. Minimzing sensor offsets
5. Information blocks from Guralp digitizers
6. Using infoblocks with Scream!
7. Determining sensor orientation
8. Units and scaling in Scream!
9. Exploring the frequency domain in Scream!
10. Expressing response information in SEED files
11. FIR filter configuration of the CMG-DM24 mk3
12. Poles and zeroes with positive normalization factors
3. Getting ready 
   
1. Pack insulation around spheres to improve thermal stability
2. Use three screws or three ceramic spacers to stabilize foot plate
3. Suspend test cable to alleviate forces associated with temperature changes
4. Connect DPG
4. Check motors 
   
1. Tilt system
2. Unlock/lock
3. mass centre
 

5. DDS 
   
1. flow of data from
1. velocity channel
1. BB
2. filtered
2. acceleration channel
1. BB
2. filtered
3. NORTEK sampling at 1 Hz
4. DPG
2. Flow of data to  
   
1. DDS
2. PGC Antelope
3. Commands from /responses to 
   
1. PGC Antelope/browser
6. Extended time testing with CNSN 
   
7. Side by side comparisons 
   
1. noise spectra all components
2. simultaneous calibrations (check for phase and amplitude differences)
3. mass positions
4. responses to real events
5. coherence
6. lack of coherence at low frequencies (convection?)
8. Confirm channel polarity using real signals, or artificially generated local signals) 
   
1. CMG-1T
2. CMG-5T
9. Clock 
   
1. NTP operation (Andreas)
2. drift rate when coasting without NTP
10. Triggered operation 
    
1. CMG-1T
2. CMG-5T
11. Tilt table for absolute calibration check? 
    
 


References 


Ideas

1. Difference component outputs from two seismometer, minimize amplitude to align them.
2. Use front end loader to thump ground near vault to check polarities
3. 0.2° leads to 43db maximum difference between ground noise and instrument noise
4. 0.01° leads to 57db, but requires a rotation of only 1.5e-3 inch on a radius of 9 inch.
 
 


Standards for Seismometer Testing, Charles R. Hutt, USGS September 1990

Parameters chosen as standards are the following

1. Sensitivity
2. Self noise
3. Bandwidth
4. Clip Level
5. Transfer Function
6. Stability
7. Cross axis coupling
8. Linearity and distortion
9. Dynamic range
10. Environmental noise sensitivity (temperature, pressure, external magnetic fields, etc.)
 


Figure 13 indicates that if the seismometers were misaligned by 0.2° (the accuracy of the magnetometer compass), the self noise derived by coherence analysis could not be less than 43db below the background signal.

Consider subtracting the output signals of two seismometers and rotating one until the difference signal was minimized.