The Manufacturing challenge
-Is it a challenge?
Research, Design, Development and
the Manufacturing of Broadband
Seismometers
Cansun Güralp
Present requirements from
broadband sensor design
Realistic Fundamental Requirements of a broadband sensor
system
– Fundamental noise level of the sensor needs to be below the Low Noise
Model
– Spurious resonance's of the design has to be well outside the required seismic
spectrum
– Frequency response
– Sensor calibration has to be an ‘absolute’ calibration
– Linearity
– Cross axis rejection
– Single sensor for each site to cover the complete Seismic spectrum
Present requirements from
broadband sensor design
Must be a feedback sensor system
– The feedback system should be able to provide different types of sensor
response to accommodate differing requirements.
– The system fundamental resonance must be controlled with feedback
– Open loop system would have substantially large sensor masses
– Open loop systems response will be different form each other, every sensor
would have to be individually trimmed to give the required response.
Practical Requirements
1.
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7.
8.
Sensor size
Operation of sensor remotely
Sensor frequency response that can be modelled with a
single transfer function
Single sensor to cover the complete seismic spectrum
Peripheral equipment to make the sensor a useful and
portable product (Borehole, Holelock, Digitisers)
Temperature of operation
Ease of set up, installation and transportability
Sensor calibration facility
Low Noise Modal and Sensor Noise (Theory)
CMG-1T Brownian Noise
Brownian Noise – Usher, Güralp 1978
Sensor Transducer and Electronic Noise – Güralp 1978
Packaging Requirements
1.
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5.
Modularity
Flexibility
Ability to provide units as Surface, Borehole and Ocean
bottom system.
Portability
Over all size of the sensor
Manufacturing – The Solution
1. Simple design
2. Clear understanding of the fundamental
principles and the relationship between
design and the theory
- Feedback, electronic design, materials,
and testing methods
3. Minimise number of components within the
design that effects the sensor performance
so that manufacturing principles can be
applied with ease.
Manufacturing Difficulties:
• Complex and multiple
materials tends to be
inconsistent with
requirements of mechanical
stability
• Complicated assembly
• Very complicated spring
systems
• Extremely expensive
machining for production
purposes
• Cannot be used as a single
sensor, i.e. Vertical and
Horizontal component
• Not a versatile design as it
tries to address a particular
solution.
Manufacturing Difficulties:
• To many parts within the
design which leads to
manufacturing difficulties.
• To many parts within the
design which leads
assembly difficulty
• Zero length spring that can
have high frequency and
long period spurious
modes of resonance's.
• Open loop system
Manufacturing Difficulties:
• Top heavy design where the
centre of gravity is too high
• Open loop system that is
likely not to meet the
required specifications
Manufacturing, Present Design:
• Does not rely on special
manufacturing techniques and
equipment
• Separate Vertical or
horizontal sensor
• Modular design
• Ease of assembly
• Reproducible in large
quantities
Manufacturing, Present Design:
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Vertical or horizontal sensor
Modular, can be integrated
with hole locks of different
design.
Ease of assembly as a system
at the installation site.
Can be a complete seismic
station, (weak + strong motion)
which the borehole sensor
incorporates Strong Motion
accelerometer.
Manufacturing, Present Design:
• Modular, can be integrated with
hole locks of different design.
• Ease of assembly as a system at
the installation site.
• Three or single jaw holelocks can
be used depending on the type of
installation
Manufacturing, Present Design:
• The design can be modified
to suite other applications.
• OBS and deep sea borehole
instrumentation, (OBH)
Manufacturing, Present Design:
• The design can be modified to suite other applications.
• Portable and easily recoverable OBS system.
Manufacturing of Broadband
Sensors
• Sensors are available in large quantities.
• To date over 2059 CMG-3 type instruments
have been manufactured
• 2003-2004 over 255 (3T / 3ESP / 3TB) and
production rate of over 719 broadband
instruments (all models).
Manufacturing of Broadband
Sensors
• Sensor response from 360 sec to 100 Hz available.
• Sensor noise from 20 Hz to >100 sec as portable sensor.
(Measured sensor noise levels not theoretical.)
• Transportable
220 mm ( 9 inches) high 168 mm diameter
Weight compact 11.5 KG
• Durability: stainless steel construction, with O rings can be
immersed in fluid for prolonged periods.
• Operation: all functions remotely controllable.
• Low power: less than 1 watt.
Production Set-up
Purpose built factory
• Isolated floor section from rest of the building.
• Building regulations
Production Set-up
Clean Rooms and Laminate Flow Cabinets:
• Investment is very costly
Production Set-up
• Rigorous internal staff training on sensor assembly and
staff training on the understanding of how NOT to build
broadband sensors.
• Internal detailed assembly documentation is essential
• Sensor test set up
• A cluster of boreholes to test borehole units
• Pits and piers
• Vault test facility with wide band transmission of data.
Production Set-up
Measurement system:
• Response measurement of large number of sensors
•
For example a 360 sec velocity sensor frequency response
can take 2 hours for 3 components.
Calibration
Automated ‘Absolute’ Calibration
Facilities
Production
Facilities
Testing: Environmental & Quality
Facilities
Automated Frequency response and Calibration
Facilities
Vault facility
Facilities
Borehole Testing
Facilities
Customers given detailed training
Design and Evolution
• Design and evolution of Sensors is REQUIRED for a mass
producible Sensor system, with continuous research and
development.
• The design staff has to be present at all times so that the
production and technical issues are resolved without delay
• The use of latest design tools must be invested in,
including training of production staff.
• The design of any Sensor has to incorporate a producible
and cost effective solution
Personnel Requirements
• Dedicated personnel must all be trained in the art of
manufacturing precision instrumentation.
• A company ethos has to be defined and accepted by all
the personnel.
• Essential to eliminate the BLACK ART associated with
broadband sensor assembly and production.
• Must be closely linked to the Research & Development
team.
• Ideally experience is required in the operation and
running of the seismic stations.
Research & Development Team
• Cybernetics, Control Systems with Mathematics and Instrument Design
PhD University of Reading
• Cybernetics, Control Systems with Engineering Mathematics
BSc University of Reading
• Mathematics and Computer Science
PhD University of Cambridge
• Physics
BA University of Cambridge
• Chemistry
PhD Cambridge
• Computer Science / Electronic and Electrical Engineering
MSc Imperial College, London / BSc University of Strathclyde
• Electronic and Electrical Engineering
BEng. Imperial College, London
Results achievable with present
design
• Sensor suitable to detect signals from Tides to 100 Hz
• Single sensor that covers the complete seismic spectrum
• Modular, can be used as a borehole, surface and OBS
type sensor system.
• Cost effective even when compared to digitisers
• Large quantities can be produced.
Sensor Noise (Testing)
To record Earth tides Sensors need very good LP performance
(5 days of raw 1 sps data)
Sensor Noise (Testing)
Mass position data
(Raw 4 sps data)
Sensor Noise (Testing)
Testing at UK factory (3 production verticals)
Sensor Noise (Testing)
Verifiable (USGS ASL)
Sensor Noise (High Freq)
Verifiable (Sandia National Laboratories)
Sensor Results from Three Component Autonomous
± 30 DEGREES self levelling OBS system with internal digitiser.
Red trace CMG-1 Z installed in OBS package, Blue trace STS1 Z installed on pier
“Quiet day”
“Stormy day”
Sensor Noise (New Sites)
New locations highlight importance of good performance (Plots – USGS ASL)
Current Research & Development
Projects
1.
2.
3.
Very high temperature Broadband sensor, continuous operation at 175 Degrees
Centigrade. CMG-3T High temperature sensor can operate at 150 degrees; this is
being improved.
Very low temperature sensor to operate at –55 degrees centigrade.
Very High Frequency feedback sensor (1Hz to 5K Hz)
4.
Unbreakable sensor for Mars, in collaboration with UCLA.
Patented
Current Research & Development
Projects
5.
Only Horizontal Acceleration responsive sensor, to remove tilt component,
from surface installations and even from borehole sensors.
6. Strong Motion Velocity sensor with long period 100 sec response up to 100 Hz
7. CMG-1T sensor system with digital output that will incorporate inherently
digital transducer.
8.
Development of new calibration techniques.
9.
Direct Digital Instrument and digital transducer with a dynamic range > 155
dB (Patent pending)
10. More than 25 % of annual turn over is fed back into R&D and invested in the
companies infrastructure.
Current Broadband Sensor
Challenge
•
Acceptance of new
concepts and ideas that
will allow complete
seismic system
simplification this being
digital output broad band
sensors.