OBS 24


OBS 24

The OBS 24 offshore seismograph, can record microseismic events occurring under oceanic sea bottom and below water depths up to 10Km. It uses atomic clock for accurate timing. The Instrument’s main structure is a glass sphere of 43 cm of diameter inside which all the electronic units and the submarine type battery packs are placed.

We have placed the 3-component seismometer outside the sphere held by a side arm that deploys the geophone once the OBS is on the sea bottom. In the tri-axial geophone case, magnetic accelerometers of type SM-6 I/O with a sensitivity of 28.8 V/m/s is used. Three perpendicular, one vertical and two horizontal sensors are placed inside a special housing to support the 600 atm. water pressure. The coupling of the overall geophone has been optimized in order to maximize sensitivity.

Technical Specifications


  • No. of channels            Four channels, three seismic and one hydrophone
  • A/D Converter              Sigma-Delta, 312Khz base rate, 24 bits resolution
  • CMRR                          Better than -100dB
  • Input Resistance           500kOhms differential
  • Sampling Rate              1-250 samples per second
  • Power                          9-18Vdc ~0.636W (53mA@12Vdc)
  • RMS Noise                   130dB @100 sps, 140dB@50 sps


      Data Recording

  • Media                            Removable Compact Flash card, up to 64 GB
  • Data file type                 CORE24 format, software format converter available
  • Additional information     Written on file header : Battery voltage, site position
  • Recording mode             Continuous
  • Recording duration         More than four months, when 4 channels continuous recording at 250sps


      Time Base

  • Type                       12 channels GPS receiver for synchronization
  • Time Accuracy         OCXO Clock : 5*10-9 sec, Atomic Clock : 1,5*10-10 sec



  • Type                   Timed or Commanded, based on electrolysis release mechanism



  • Bandwith             0.2Hz - 98Hz
  • Sensitivity           1000V/m/sec
  • Channels             3 seismic, Z(Vert)-Y(North)-X(East), 1 hydrophone



  • Gross OBS Weight      58 kg
  • Net OBS Weight          -8 kg (8kg buoyancy without the metallic base)



  • Temperature range        -20 to + 70 0C
  • Depth                             Up to 12.000 m