KSS32-M
The Marine Gravity Meter KSS32-M is a high performance instrument designed for marine geophysical research projects, including oil prospecting and basic research worldwide. Straight line technology together with the best precision mechanics and state of the art electronics enable highly accurate gravity measurements. As a marine Gravity Meter it is free from any Cross-Coupling errors.
Several embedded microprocessors together with sophisticated software programmes provide very easy handling. Important corrections, like Eötvös-effect and curve compensation can be applied in real time. Data from the ship’s navigation system can be fed into the Gravity Meter by interfaces. The instrument is furnished with a variety of interfaces to connect to other instruments and to have their data stored. The software includes a number of digital filters to apply to the data. The software offers corrections of the free-air and Bouguer anomalies. In case of a problem the entire system will be turned off and arrested to protect the measuring system even in severe sea conditions.
The KSS32 M – Sensor has 3 different modes. There is a mode for measuring, one for the Ball Test to check if the sensor works correct and one mode for transport. This latter one is called cage mode. In case of a power failure the sensor uses mechanically stored energy to bring itself into cage mode. This important safety feature protects the sensitive internal mechanics of the sensor reliably and efficiently in both transport and emergency scenarios.
The KSS32 M – stabilized platform, respectively its highly accurate and fast responding gimbal system can also be caged to prevent unintended movements in case of a power failure or when the gyro-based stabilization is not active. Therefore the system is equipped with an uninterruptible, battery-free and maintenance-free supply (UPS) that allows the system to emergency-shutdown itself whenever necessary.
Real time gravity measurements are provided via standard interfaces like serial RS232 and Ethernet. This allows to easily run your own data acquisition and/or data processing independent from the sensor location.
(Remote Control) The Ethernet interface additionally provides remote access to KSS32 M data acquisition and control software (DACQS) providing a graphical user interface for quick data analysis, measurement monitoring and full system (platform and sensor) control.
The sensor of the KSS32 M system is protected against temperature gradients in the environment by a double-walled vacuum flusk, a so-called Dewar-vessel. Additionally, a grid of heating wires encloses the Dewar-Vessel. This heating is controlledby the sensor control-electronics to stabilize the internal temperature at a constant level of approximately 50°C and to guarantee internal variation in temperature of less than 0.01°C, minimizing material expansion/dilatation and conductibility. The result is the known high accuracy, very good stability and the reliable measurements of the KSS32 M sensor.
KSS32-M Brief Description
The BGGS Gravitymeter KSS32-M offers many advantages:
- High precision instrument. Accuracy better than 0.5 mGal.
- Very low drift.
- Worldwide measuring range.
- Straight line sensor without Cross-Coupling effect.
- Possibility of highly accurate and linearized measurements for up to 0.23 g (230 000 mGal) of vertical acceleration.
- Short recovery after profile changes if navigation data are available.
- Valuable readings during turn-manoeuvre if accurate navigation data are available.
- Operation at different sea states will be ensured by selection of appropriate filtering. Measurements are made possible even at rough sea conditions.
- Safety precautions for sensor and gyro platform in case of power breakdown.
The entire system can be operated and controlled via a standard computer/notebook and the BGGS application software DACQS:
- Start-up procedure.
- Run-down procedure.
- Safety routines.
- Application of parameters.
- Permanent system tests.
- Display and visualization of monitor data and status.
- NMEA-link to navigation and other marine instruments.
- Data from echo-sounder (if available)
- Data from magnetometer (if available).
Technical
data
Accuracy, during straight course
| Vertical Acceleration | Dynamical¹ (RMS) | Effective² (RMS) |
|---|---|---|
| less than 15.000 mGal | 0,5 mGal | 0,2 mGal |
| 80.000 – 250.000 mGal | 2,0 mGal | 0,8 mGal |
Accuracy, during turning manoeuvre
| Vertical Acceleration | Dynamical¹ (RMS) | Effective² (RMS) |
|---|---|---|
| less than 15.000 mGal | 2,5 mGal | 2,5 mGal |
¹ Accuracy without data processing
² Accuracy after data processing
| Sampling | 1 reading per second |
| Drift rate | 3 mGal/month |
| Range | 20.000 mGal (worldwide) |
| Accuracy of Scale Factor | 0.5% |
| Platform Roll | +/- 40° |
| Platform Pith | +/- 40° |
| Power Supply | 100 -230 Vac / 50 – 60Hz |
| Power rating | 400 VA max. |
| Environment | Temperature: +10°C to +35°C Gradient of Temperature: less 2°C per hour Humidity: 30% to 70 % |
KSS32-M system overview
Function principle of sensing element Straight Line Sensor GSS32
The axially symmetric spring-mass arrangement at the STRAIGHT LINE SENSOR of the BGGS KSS32(-M) gravimeter is shown schematically. A 36g TUBE-MASS is constrained to move vertically, so in contrast to a horizontal beam system, the sensor is essentially not influenced by cross-coupling between horizontal and vertical accelerations, e.g. of the vessel. The displacement of the tube is measured by a CAPACITIVE TRANSDUCER at the top. Motion is minimized by a feedback loop consisting of two windings of a COIL moving in the field of a strong permanent MAGNET at the bottom of the tube. Gravity changes are derived from currents generated in the moving coil.