Portable Cesium  Magnetometer/Gradiometer - Model G-858/G

Land Mag Products

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The G-858 MagMapper  uses a graphical interface to make survey design and data acquisition quick and efficient.  Various modes of operation allow the user to custom design a survey grid for their  particular needs. The operator also has the ability to view his/her position on the grid  and the current data profile during the survey. Sensitivity, resolution, and recording  rate of the cesium magnetometer are user selectable.

G-858 data acquisition offers  either continuous or discrete station recording. The high sampling rate of the instrument  in continuous mode allows the operator to survey an area at a fast walking pace. A wider  search radius can be achieved by using a gradiometer configuration. As a result, over-all  costs are inherently lower while data quality remains high.

 The G-858 is designed to interface easily with standard computers and peripherals.  Geometrics encourages clients to provide their own processing computer hardware. Upon the  client's request Geometrics will provide a complete and fully integrated processing  station at a nominal price.

Features:
  • in-field coordinate mapping system
  • high sensitivity: detects single drum at 3m
  • Immediate User Feeback: display coordinate grid, survey direction and 5 stacked profiles of mag data
  • easy to use: produce hard-copy maps within minutes of connection to PC
  • options: symultaneous vertical or horizontal gradiometer, GPS positioning, target analysis software

The G-858 MagMapper system comprises a belt-mounted display/logging console connected to a  cesium sensor mounted on a handheld counterbalanced staff. The console contains  electronics to acquire magnetic field data with position and display it on an LCD screen  for review and edit. The console stores high volumes of data in memory. Following the  survey the data is transmitted at high speed to a processing computer for detailed  analysis.

A basic  software package - MagMap, is supplied as an integral part of the G-858 system. It  provides:

  • - Transfer of the raw data to the client PC;
  • - Standard corrections for position errors, transients, and time varying errors (diurnal);
  • - Repositioning, linear interpolation and format corrected data into X,Y,Z ASCII columnar  values for use with various contouring programs

Specifications:

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

Heading  Error: +/- 1 nT

Operating Range: 20,000nT to 100,000 nT

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

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.

Data  Storage: Nonvolatile RAM with capacity for 8 hrs. of Magnetometer time, event marks,  field notes, location, or 3 hrs. of Gradiometer and GPS at maximum sample rates.

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. 0.02nT at 0.5 sec cycle rate
  4. 0.01nT at 1.0 sec cycle rate

Visual  Display: A 320x200 graphic LCD, daylight visible with selectable outputs for:

  1. Data display
  2. System setup functions
  3. Survey setup functions
  4. Survey monitoring
  5. System diagnostics

Data Output:  Three wire RS232 standard serial port,  optional continuous real time transmittal of data via RS232 to PC. Total memory output  transfer time less than 5 minutes at 115,200 baud

Battery  Life:

  1. 24 VDC rechargeable gel cell, 6 hrs. Magnetometer or 3 hrs. Gradiometer usage.
  2. Internal backup battery for clock and nonvolatile RAM

Operating Temperature: -25o C to +50o C (-13o F to +122o F

Water  Tight: To 3 ft. (0.9 m) depth

Shock: Drop 3 ft. on a hard surface without damage.

Console  Magnetic Effect: Less than 1nT at 4 ft. from sensor.

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