Trillium Compact Ocean Bottom Seismometer

• Summary
  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.
  
• Benefits
  • 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)
• Specifications

  TECHNOLOGY

  Topology	Symmetric triaxial
  Feedback	Force balance with capacitive transducer
  Mass Centering	Not required

  PERFORMANCE

  Self-noise	See graph
  Sensitivity	750 V·s/m nominal ±0.5% precision
  Off-axis Sensitivity	±0.5 %
  Bandwidth	-3dB points at 120 s and 100 Hz
  Transfer Function	Lower corner poles within ±0.5% of nominal provided High-frequency response within 1dB of nominal No peak in response at high frequency
  Clip Level	26 mm/s from 0.1 Hz to 10 Hz
  Parasitic Resonances	None below 100 Hz
  Operational Tilt Range	±2.5° without re-leveling

  LEVELING AND ORIENTATION

  Technology	Dual degree-of-freedom motorized gimbals Jam-free mechanism Kinematic design preserves full seismometer performance
  Clamping	Active, sequenced by gimbals processor
  Range	>±180° relative to upright case
  Accuracy	Levels to within ±0.5° of true vertical
  Leveling Initiation	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
  Magnetometer	3-component, mounted on and leveled with seismometer
  Case and Sensor	Tilt orientation of vessel and sensor recorded throughout
  Inclinometers	deployment

  DIGITAL INTERFACE

  Type	RS-232 compatible Serial Line Internet Protocol (SLIP) On board Web Server, standard HTTP
  Leveling	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
  Mode Selection	Short Period/Long period
  Calibration Channel Selection	Off, enable all, U, V, or W
  Firmware	Update Firmware

  DATA OUTPUTS

  On Request	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
  Leveling Log	Every leveling event is logged in non-volatile memory Full before-and-after state-of-health is logged
  State-of-Health Log	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	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
  Diameter	170 mm
  Height	258 mm, not including connectors
  Weight	12.9 kg on land, 7.1 kg in water
  1800m Variant
  Enclosure	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
  Diameter	170 mm
  Height	258 mm, not including connectors
  Weight	8.7 kg on land, 3.01 kg in water

  CONNECTORS

  Main Connector	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
  Secondary Connector	4-pin female, VSG-4-BCL rubber-molded glass epoxy
  (Auxiliary/Diagnostic)	Serial RS-232 port Auxiliary control input
  Vacuum/Pressure Port	¼” male quick disconnect with shutoff Vent for evacuation and servicing

  POWER

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

  ENVIRONMENTAL

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

  
  

  Specifications subject to change without notice

• Performance