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Portable Proton Magnetometer

Geometrics Model G-856

The G856 provides a reliable, low cost solution for a variety of magnetic search and mapping applications.  Single key stroke operation means  the G856AX can be operated by non-technical field personnel or used in teaching environments. The G856AX uses the well proven proton precession technology, 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 Bureau of Standards.
Current primary application for the G-856AX is as a base station system for monitoring and recording of the earth's diurnal field shift.  This base data is downloaded into MagMap2000 for automatic correction of G-865AX, G-858 or airborne survey data.  A standard accessory package with external power and 50 ft. sensor cable is available for base station operations.

The G-856AX is also used in mapping geological structures, for mineral exploration, magnetic search for industrial, environmental or archaeological targets.  The optional gradiometer attachment gives greater resolution and noise immunity for conducting searches in industrial or 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.

A thoroughly well proven design (over 2,500 units sold), excellent performance and the lowest price professional system are key features of the G-856AX. Combined with the ease of use, user friendly download/editing software, and readily available commercial contouring programs, the G-856AX represents a complete magnetic surveying package generating high quality data for budget conscious users.


Display: Six digit display of field to 0.1 gamma, or time to nearest second. Three digit display of station, day, line number, battery voltage, or signal strength.
Resolution: Typically 0.1 gamma under average conditions, may degrade in weak fields, high gradients, or noisy conditions.
Accuracy: 0.5 gamma
Tuning: Auto or manual, range 20,000 to 90,000 nT
Gradient Tolerance: 1000 nT/meter
Cycle Time: 3 sec to 999 sec. standard; can be manually selected as fast as 1.5 sec cycle time
Read: Manual or auto cycle for base station use
Data storage: 5,700 readings in portable mode, 12,000 in base station mode. Power failure will not cause any data loss.
Display: Six digit display of field/time, three digit auxiliary display of line number, day
Digital Output: RS-232, 9600 baud
Input: Will accept external cycle command
Power: Rechargeable Battery Pack (2) plus charger included
Weight: Instrument console - 6 lb., Staff & Sensor - 6 lb.


The portable gradiometer option employs two sensors, samples and stores readings from each in quick succession, and uses the difference between the readings to more precisely locate shallow objects. Gradient information is particularly useful for shallow search and survey applications because it can quickly define the depth and location of objects without the need for a base station. The gradiometer accessory consists of a gradiometer adaptor switch, a second proton precession sensor, cables, special sensor staff, and MAGPAC IBM-compatible software for automatic diurnal correction of total field data as well as filtering, contouring, and other data processing operations. The gradiometer has an accuracy of 0.1 gamma or 0.02 gamma per foot for sensor spacing of greater than 5 feet. When used in the gradient configuration, the system is capable of storing up to 2850 pairs of readings. The instrument functions as a regular magnetometer when the adaptor switch is not used.

U.S. Domestic Prices

G-856 PROTON MAGNETOMETER.................................$5,950.00
GRADIOMETER ACCESSORY.....................................$2,560.00
GRADIOMETER CARRYING CASE...................................$305.00
BASE STATION TRIPOD KIT.....................................$330.00
Includes tripod base for use with existing magnetometer 
sensor and staff sections

Contact ASC Scientific at for additional information on the G-856 and accessories.

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ASC Scientific
2075 Corte del Nogal, Suite T, Carlsbad, CA  USA 92011 - Tel. (800) 272-4327 - Fax.  (760) 431-0904