Trillium Compact Ocean Bottom Seismometer

The Trillium Compact Ocean Bottom Seismometer (OBS) is available in a titanium vessel for deployments to 6000m in depth and an optional aluminum vessel for shallow water deployments to 1800m.  The Trillium Compact OBS also features a robust leveling gimbal that operates over a full 360°range allowing the seismometer to auto-level from all orientations. Leveling control is internal and can be scheduled or "as necessary" based on instrument tilt and mass position values.  Both variants offer the full performance of the land based Trillium Compact broadband seismometer including its exceptional dynamic range and low noise floor.   The system employs two separate connections: the primary analogue connection as well as a digital connection.  The digital connection is intended for final system verification prior to deploying the OBS overboard without disturbing the primary connection. Internal state-of-health data provides valuable information on leveling cycles, leveling corrections and case orientation, information that can be used to understand the conditions experienced on the ocean floor leading to improved experiment design. 

  • The precise, kinematic 360°gimbal auto-levels from any orientation ensuring successful deployment and implementation
  • SoH outputs include case orientation, providing a powerful data set for optimizing deployment techniques
  • The low profile design minimizes ocean current induced noise effects
  • Battery costs are reduced due to the ultra-low power consumption of just 180mw
  • A high performance, 120 second broadband seismometer that integrates with existing short period or mid-band infrastructure (platforms, power systems and digitizers)

      

TECHNOLOGY

  

Topology:
Feedback:
Mass Centering:

Symmetric triaxial
Force balance with capacitive transducer
Not required

PERFORMANCE

  

Self-noise:
Sensitivity:
Off-axis Sensitivity:
  Bandwidth:
Transfer Function:


Clip Level:
Parasitic Resonances:
Operational Tilt Range:

 See graph
750 V·s/m nominal ±0.5% precision
±0.5 %
-3dB points at 120 s and 100 Hz
Lower corner poles within ±0.5% of nominal provided
High-frequency response within 1dB of nominal
No peak in response at high frequency
26 mm/s from 0.1 Hz to 10 Hz
None below 100 Hz
±2.5° without re-leveling

LEVELING AND ORIENTATION

Technology:


Clamping:
Range:
Accuracy:
Leveling Initiation:





Magnetometer:
Case and Sensor
Inclinometers

Dual degree-of-freedom motorized gimbals
Jam-free mechanism
Kinematic design preserves full seismometer performance
Active, sequenced by gimbals processor
>±180° relative to upright case
Levels to within ±0.5° of true vertical
Some or all of:
- configurable delay after power on
- configurable three-stage periodic
- delay intervals configurable from seconds to monthsScheduled leveling checks do not disturb seismic data recording when sensor is level
                                                                 
3-component, mounted on and leveled with seismometer
Tilt orientation of vessel and sensor recorded throughout
deployment

DIGITAL INTERFACE

  

Type:

Leveling:


Mode Selection:

Calibration Channel Selection:
Firmware:

RS-232 compatible Serial Line Internet Protocol (SLIP)
On board Web Server, standard HTTP
Initiate immediate leveling
Automatic cycle mode (post power-on, periodic, as-needed)
Automatic cycle parameter selection (delay with interval time selection, maximum number of attempts):   XYZ/UVW
Short Period/Long period
Off, enable all, U, V, or W
Update Firmware

DATA OUTPUTS

  

On Request:











Leveling Log:

State-of-Health Log:

Independent mass position values
Instrument temperature
SOH
Magnetometer readings
Case orientation (with respect to vertical)
Seismometer orientation (with respect to vertical)
Download state-of-health (SOH) log
Erase SOH log
Download custom information
Factory sensitivity and sensor response data
User calibration data (poles and zeros)
Instrument serial number and firmware revision
Every leveling event is logged in non-volatile memory
Full before-and-after state-of-health is logged
Scheduled interval logging of SOH, including:
·         Time from power-on
·         Seismometer mass positions
·         Vessel and seismometer orientations
·         Magnetometer readings
·         Temperature
Capacity for more >2 years of twice daily level checks and SOH logging

PHYSICAL

 
6000m Variant
Enclosure:



Diameter:
Height:
Weight:

1800m Variant
Enclosure:



Diameter:
Height:
Weight:
Titanium, non-painted cylinder
All connectors on top end cap
End caps removable for O-ring servicing
Dual O-ring seals on each end cap
170 mm
258 mm, not including connectors
12.9 kg on land, 7.1 kg in water
 

Aluminum, anodized, enamel painted cylinder
All connectors on top end cap
End caps removable for O-ring servicing
Dual O-ring seals on end cap
170 mm
258 mm, not including connectors
8.7 kg on land, 3.01 kg in water

CONNECTORS

  
Main Connector:




Secondary Connector:
(Auxiliary/Diagnostic):

Vacuum/Pressure Port:		 12-pin female, VSK-12-BCL rubber-molded glass epoxy
40V peak-to-peak differential seismic signal plus ground (3 channels)
Serial RS-232 port (Rx, Tx, GND)
Calibration voltage input
Power input and return
4-pin female, VSG-4-BCL rubber-molded glass epoxy
 Serial RS-232 port
Auxiliary control input
¼” male quick disconnect with shutoff
Vent for evacuation and servicing

POWER

  

Supply Voltage:
Power Consumption:
Protection:

9 to 29 VDC isolated
<180 mW typical (leveled, quiescent)
Reverse-voltage and over-voltage protected
Self-resetting over-current protection
Unit can be powered on for descent and ascent

ENVIRONMENTAL

  

Operating Temperature:
Storage Temperature
Shock:
Transportation:
Magnetic:

-20ºC to +60ºC
-40ºC to +70ºC
100g half sine, 5 ms without damage, 6 axes
No seismometer mass lock required prior to deployment and through full experiment cycle
Insensitive to natural variations of the Earth’s magnetic field