Geometrics G-856AX Proton Magnetometer - A Robust, Reliable and Affordable Magnetic Mapping System


G-856AX Features

  • High resolution - accurate to within 0.1 gamma
  • Easy operation - automatically tunes, reads, and displays total field at the touch of a button. Beeper sounds when keyboard is used
  • Expandable memory - stores and accesses up to 5,700 field readings or 12,000 base station readings
  • Convenient data recall - stored readings instantly available, including time, date, and station number
  • Automatic data processing - download to your PC for on-line processing, including correction for time variations, averaging, filtering and drawing profiles
  • Versatile - portable search and survey magnetometer, gradiometer or base station recorder
  • Works anywhere - unaffected by orientation or environment. Sealed, scratch-resistant keyboard is weatherproof
  • Easy to carry - console weighs only 2.7kg with D-cell batteries installed
  • Comes complete - supplied with sensor, staff, chest harness, batteries, carrying/shipping case, and manuals


G-856AX Description

G856 Components.jpg (11544 bytes)Accurate, lightweight and versatile, the G-856AX is well-suited to a wide range of applications, including geologic mapping, mining, fault location, archeology and magnetic search.

The Model G-856AX Proton Magnetometer automatically measures the absolute value of the earth's magnetic field to a resolution within 0.1 gamma. Reducing the number of written notations required in the field, the internal digital memory permits easy retrieval of field readings either manually or via download to PC. Using a PC the G-856AX can be used to produce profiles, to make corrections for diurnal time variations, and for data averaging or filtering. A built-in Julian clock monitors the exact time of each reading and special function buttons protect against accidental erasure of readings. The G-856AX also incorporates a unique "Brazil Switch" that provides convenient adjustment for the weaker signals typically encountered near the magnetic equator.

Simplified Operation - Designed for easy use by non-skilled personnel, the G-856AX combines high accuracy with convenient, push-button operation.

Personal Computer

The G-856AX is compatible with PC's using RS-232 (serial) input. With the aid of a PC, the G-856AX permits a wide range of processing styles. Averages may be run to filter out near-surface magnetic anomalies, or regional gradients may be removed to emphasize local information. If data from a separate base station has been entered into the computer, errors from temporal variations in the magnetic field may be removed and interpolated data can be generated to simplify contour mapping, or a complete map can be produced. MagMap96, supplied with the G-856AX, handles all basic processing, including parsing of GPS info to the magnetic data, and export of data to Surfer format for contouring and 3-D data display.

MagMap for Windows, a basic software package, is supplied as an integral part of the G-856AX 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.
  • Parsing of GPS data to magnetic data set


  • DISPLAY: Six-digit display of magnetic field to resolution of 0.1 gamma or time to nearest second. Additional three-digit display of station, day of year; line number; battery voltage or signal strength.
  • RESOLUTION: Typically 0.1 gamma in average conditions. May degrade to lower resolution in weak fields, noisy conditions or high gradients.
  • ACCURACY: One-half gamma, limited by remnant magnetism in sensor and crystal oscillator accuracy.
  • CLOCK: Julian clock with stability of 5 seconds per month at room temperature and 5 seconds per day over the temperature range of - 20 to + 50 degrees Celsius.
  • TUNING: Automatically tunes for maximum signal strength after each reading. Tuning may be manually adjusted to compensate for high gradient shifts and for changes in length of sensor cable. Tuning range covers 20 to 90 kilogammas.
  • GRADIENT TOLERANCE: Tolerates gradients to 5000 gammas/meter. When high gradients truncate count interval, maintains partial reading to accuracy consistent with data. Sounds audio alarm in high gradients or when signal is weak.
  • CYCLE TIME: Complete field measurement in three seconds in normal operation. Internal switch for faster cycle (1.5 seconds) at reduced resolution or slower cycle for improved signal. Auto-cycle time for base station operation can be reduced to 2 seconds.
  • MANUAL READ: Takes reading on command. Will store data in memory on command at operator's discretion.
  • SELF-CYCLE: Internal switch will cause the instrument to self-cycle, storing automatically for time dependent measurements. Available intervals are 4 to 999 seconds in one-second increments selected by push buttons.
  • MEMORY: In portable mode stores over 1,400 readings with time of reading and station number. In base station mode, stores over 2,500 readings with Julian date and time of reading.
  • OUTPUT: Standard RS-232 (serial).
  • INPUTS: Will accept an external sample command and will synchronize reading with another G-856AX.
  • BEEPER: Sounds once when a key is touched, three times after data have been transferred through RS-232 port, and five times in high gradients or when signal is weak.
  • SPECIAL FUNCTIONS: An internal switch allows lengthening or shortening polarization time and count time to improve performance in marginal areas, improve resolution, shorten cycle time, increase battery life, and to perform a 3-point average. 
  • Instrument console: 18 x 27 x 9 cm; 2.7 kg.
    Sensor: 9 x 13 cm; 1.8 kg.
    Staff: 3 cm x 2.5 m; 1 kg.

  • ENVIRONMENTAL: Meets specifications from 0 to 40 degrees Celsius. Operates satisfactorily from - 20 to 50 degrees Celsius. Weatherproof.
  • POWER: Operates from 8 D-cell flashlight batteries (or 12 volts external power). May be operated at 18 volts external power to improve resolution. Power failure or replacement of batteries will not cause loss of data stored in memory. Battery voltage measured and displayed during polarization.
  • STANDARD ACCESSORIES: Sensor, Staff, Chest Harness, Two sets of Batteries, Operating Manual, Applications Manual for Portable Magnetometers.
  • OPTIONAL ACCESSORIES: Gradiometer Configuration, RS-232 Interface Cable, Cold Weather Battery Belt.


G-856AX Options

  • Gradiometer - A gradiometer configuration  is available with the addition of a second sensor and staff attachments. Includes a secong sensor, staff inserts & a remote switch. Unit sequentially reads each sensor at 3 second intervals.
  • Rechargeable Battery Kit - Provides gel cell batteries with internal mounting plate & battery charger.


G856 Gradiometer.jpg (12119 bytes)

G-856AX being used in gradiometer mode


For more info or pricing, follow the Geometrics pointer at the bottom of this page or contact Red Dog Scientific Services , authorized representative for South / Southern Africa