G-857 Magnetometer

The newly re-engineered G-857 provides a reliable, low cost solution for a variety of magnetic search and mapping applications. Single key stroke operation means the G-857 can be operated by non-technical field personnel or used in teaching environments. The G-857 uses the well-established proton precession method, allowing accurate measurements to be made with virtually no dependence upon variables such as sensor orientation, temperature, or location. The unit provides a repeatable absolute total field magnetic reading, traceable to the National Institute of Standards and Technology. The unit offers new features such as GPS time synchronization, GPS positions and in-field navigation with a hand held Garmin GPS.


The G-857 is ideal for mapping geological structures, for mineral exploration, or magnetic search for industrial, environmental or archaeological targets. The optional gradiometer attachment gives greater resolution and noise immunity for conducting searches in high cultural noise environments. Simple operation, large digital data storage capability, and the inclusion of MagMap2000 data transfer and editing software provides a system well suited for both teaching and survey applications.
The automated cycling option with long sensor cable and external power connection allows the G-857 to be used as a base station instrument for the measurement of diurnal changes in the Earth’s magnetic field. Diurnal correction data is then downloaded using MagMap2000 and can be applied to either land or airborne magnetometer data.

Superior Data Editing Software:

MagMap2000 allows rapid download of the data from the G-857 to a PC. Data can be diurnally corrected, profile lines and X, Y or GPS positions displayed and edited, noisy readings filtered and QC plots of profiles, 2D contour plots made. Data can be exported to Surfer, Geosoft or MagPick (high end processing software free from Geometrics) for more sophisticated final maps and analysis including Google Earth overlay maps. The software requires Windows XP, 7, 8 or 8.1 operating system.

MagMap2000 display screen

MagMap2000 display screen

The G-857, based on the popular G-856AX, provides excellent performance and is the lowest priced professional magnetometer system available. With simple operation, user friendly download/editing software, and format read for available commercial contouring programs, the G-857 represents a complete magnetic surveying package generating high quality data for budget conscious users.

MagMap2000 display screen

G-857 Base Station and Optional Garmin GPS


  • Resolution: 0.1 nT
  • Accuracy : Absolute 0.5 nT
  • Clock: Julian date, accuracy 5 sec per month.
  • Tuning: Auto or manual, range 20,000 to 90,000 nT
  • Gradient Tolerance: 1000 nT/meter
  • Cycle time: 1.6 sec to 999 sec standard
  • Read: Manual, or auto cycle for base station use.
  • Memory: 65,000 field or base station readings
  • Display: Six digit display of field/time, three digit auxiliary display of line number, day
  • Digital Output: RS-232, switch selectable to 115200 baud.
  • Input: Will accept external cycle command.
  • Physical Console: 7 × 10.5 × 3.5 inches, (18 × 27 × 9 cm) 6 lbs (2.7 kg)
  • Sensor: 3.5 × 5 inches ( 9 × 13 cm) 4 lbs (1.8 kg
  • Environmental: Meets specifications within 0 to 40 C Will operate satisfactorily from -20 to 50 C
  • Power: 12 Volt rechargeable Gel Cell

Standard Accessories:
Sensor, Staff, Chest Harness, Two sets of batteries, RS-232 cable, USB Serial adapter, Operations manual, Applications manual, MagMap2000 software

Gradiometer attachment. External power/RS-232/sensor cable, rechargeable battery and charger set, Garmin Oregon 450 GPS

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