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G-880 Marine Cesium Magnetometer/Gradiometer

Geometrics  presents a new high resolution marine Cesium magnetometer system for all types of  production surveys. Simultaneous readings may be obtained from up to 6 individual sensors  through cable lengths to 2500 ft. System features include very high  sensitivity  measurements of total field and gradient combined with rapid sampling.

A new Larmor counter provides direct connection to a host CPU for integrated SideScan  or ROV installations.  The G-880 is completely digital, unaffected by shipboard noise,  easily deployed and simple to operate.

A key  element in the high performance of the system is the  conditioning and the counting of the  Larmor signal. Using a proprietary design mounted into the electronics pressure vessel,  sensitivity, measurement rates, number of sensors and data format are  selected by commands  from the vessel. Counters from multiple sensors may be concatenated together to provide a  sequential stream of RS232 data for transmittal throug

Download G-880 Data Sheet
h the tow cable.

Features:
  • Sensitivity 0.02nT at 10 samples per second - selectable.
  • Multi-sensor gradiometer arrays for precise search or diurnal corrected total field.
  • Quick-connect integration to SideScan Sonar systems with simultaneous data display.
  • Tow cable lengths to 2500 ft. - digital data immune to shipboard noise.
  • Petroleum - oceanographic - or search surveys.
  • Includes sensor depth data - calibration of absolute accuracy - world wide operation.

Specifications:

Operating Principle:Self-oscillating split-beam Cesium  Vapor  (non-radioactive Cs133) with automatic hemisphere switching.

Operating  Zones:For highest signal-to-noise ratio, the sensor long axis should be oriented at  45o, +/- 30o to the earth's field angle, but operation will continue  through 45o, +/- 35o.

Operating Range:17,000nT to
100,000 nT

Gradient  Tolerance:> 500nT / inch; >20,000nT / meter

Heading Error:+/- 0.5 nT

Data Output:Three wire RS232, magnetics, up to 6 A/D channels for other sensors if  present

Sensitivity:90% of all readings will fall within the  following Peak-to-Peak envelopes:

  1. 0.05nT at 0.1 sec cycle rate
  2. 0.03nT at 0.2 sec cycle rate
  3. 0.01nT at 1.0 sec cycle rate

Larmor  Counter:

  1. Integrated into sensor electronics in 'fish'
  2. Ref Osc: Nominal 22 MHz
  3. Output data concatenated with other counters or data sources if present
  4. A/D converters: 3 single and 3 differential, 12 bit resolution.
  5. Control functions: Keyboard commands from surface

System Components:

Power Supply:

  1. Converts 115/220 50/60Hz AC to 28 to 32 VDC, 150 W
  2. Provides cable junction for power & data
  3. 8 x 9 x 4.5 inches, 6 lb

Environmental:

  1. Operating / Storage Temperature: -45oC to +60o C (-40o F to +140o F)
  2. Depth: Pressure vessels in 'fish' rated to 4,000 ft (increased depth possible upon  request)

Tow Cable:

  1. Shielded twisted pair of #12 conductors with 8 separate #20 conductors
  2. Strain member: Kevlar, 10,000 lbs breaking strength
  3. Maximum working load: 1250 lbs
  4. Outside diameter: 0.65 inch
  5. Bending diameter: 24 inch
  6. Weight: Air: 215 lbs per 1000 ft. Water: 70 lbs per 1000 ft
  7. lengths selectable to 2,500 ft (762 meters)

Sensor  'Fish':

  1. Heavy duty filament wound fiberglass,free flooded with stabilizer ring-fin assembly
  2. Length:83 inches (cable stiffener and bulkhead termination adds 16 inches to length
  3. Body outside diameter: 4.5 inches
  4. Ring-fin outside diameter: 14.25 inches
  5. weight in air: 38 lbs; in water: 12 lbs
  6. Depth transducer installed

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