SEA III

SeaIII Gravity

Category： Marine Gravity

Model： SEA III

Brand： Micro-g LaCoste

Quantity： 1

Instrument： Shipboard Instrument on R/V New Ocean Researcher 1

Equipment Condition： Normal

Maintenance Manager

Chang Hsuan-Cheng
Technician III
(02)3366-7282
samsonchang@ntu.edu.tw

Instrument Expert

Function Description

SEA III Marine Gravity System

The SEA III Marine Gravity System is the latest generation of dynamic marine gravimeters from Micro-g LaCoste. Continuing LaCoste & Romberg's design tradition of over 60 years, it employs zero-length spring tension and beam-speed sensor technology, optimized specifically for marine gravity measurement applications.

System Features:

  • Reduced Size and Weight: The sensor and gimbal platform's size and weight are reduced by 30%. The overall frame size is reduced to 56 x 61 x 76 cm, with a weight of 109 kg.

  • New Slip Ring Technology: The gimbal platform uses new slip ring technology to enhance stability and reliability.

  • Temperature Control: A dual-layer furnace temperature control system ensures that the sensors and electronic equipment operate at a stable temperature.

  • High-Precision MEMS IMU: The platform control utilizes a high-precision MEMS IMU, improving measurement accuracy.

  • Software Features: SEA III software offers data logging, total correction (TC), quality control gravity (QC Gravity), cross-coupling correction (CC), and supports user-selectable filters and basic calibration functions.

Borrowing Rules

Please contact the equipment technician.

Equipment Description

SEA III Marine Gravity System Specifications

Parameter Specification
Sensor Type Zero-length spring tension / beam velocity sensor with feedback control
Static Measurement Range 20,000 mGal (Global Range)
Dynamic Measurement Range ±0.5 g
Long-Term Drift (Operating State) 0.1 mGal / day
Resolution 0.001 mGal
Static Repeatability (Calibration Line) 0.25 mGal
Dynamic Repeatability 0.25 mGal (Lateral 50,000 mGal)
0.50 mGal (Lateral 100,000 mGal)
0.50 mGal (Vertical 100,000 mGal)
Platform Pitch Range ±35°
Platform Roll Range ±35°
Platform Period 4 minutes (Damping Coefficient 0.707)
Platform Control High Precision MEMS IMU
Data Logging Rate 20 Hz or 1 Hz (Selectable)
Digital Output RS-232 / USB
Additional Outputs Sensor temperature, pressure, three-axis linear acceleration, three-axis gyroscope, GPS positioning
Dimensions (Including Frame) 56 x 61 x 76 cm
Weight (Including UPS and Electronics) 109 kg
Temperature Control System Double-layer furnace temperature control, temperature control for electronics and accelerometer
Software Control SEA III GUI Application (Windows System)
Data Format Supports ASCII output, can be stored on hard drive

Maintenance & Attendance Records

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Operation Manual

Installation and Operation:

  • Lightweight Design: The system's weight and volume are reduced by 30% compared to previous generations.

  • Locking Gimbal: The locking gimbal enhances stability and reduces vibration effects.

  • Windows GUI Software: Provides data logging, filtering, total compensation calculations, and quality control functions.

Power and Environmental Adaptability:

  • Operating Temperature: 0°C to 50°C.

  • Power Requirements: 70W (normal operation) / 250W (startup).

  • Dimensions: 56 x 61 x 76 cm, weight 109 kg.

Notes:

  • Instrument Warm-Up: Typically requires more than 24 hours of warm-up time to maintain a stable temperature for accurate results.

  • Boat Speed Requirements: Maintain a stable cruising speed to minimize acceleration interference.

  • Weather Limitations: Avoid measurements in strong winds and waves to prevent excessive platform sway, which could damage the sensor.

  • Regular Calibration: Use land-based reference points or compare with known values for calibration.

  • Data Post-Processing: Tidal, drift, boat speed, Eötvös, and other compensations are necessary for data correction.

Application Areas:

  • Geophysical and Geological Surveys

  • Marine Gravity Mapping

  • Oil and Mineral Exploration

  • Earth Gravity Field Modeling