The model G-823A Cesium Magnetometer provides unmatched versatility of performance, size, function, and cost-effectiveness for larger scale aerial-based magnetic surveys. It can also be used as land portable system.

In addition to the magnetometer measurement, the internal CM-201 counter also includes Julian time/date, a provision to accept an external sync pulse, and six A/D converters for digitizing and recording signal amplitude, radar/barometric altimeter, EM or other analog data. The transmission format of all functions is selected by software command and may be customized for each job.

The G-823A meets the highest vibration and temperature standards for airborne, land, or marine surveys. Custom-length cables and special packaging are available for each of these applications. Critical heading error performance is documented and supplied for each G-823A system.

Geometrics offers a complete system including magnetometer, GPS navigation, data logging and display software, post-acquisition data processing software, and training. Expand your Magnetometry surveying capabilities with the versatile multi-sensor array capable G-823A Cesium Magnetometer!


Features and benefits

  • Versatile Multi-Sensor Array Capability: This instrument can be used in fixed wing, helicopter or land applications to fit any surveyor’s needs.
  • Highest Sensitivity: Pick up the smallest variations in the magnetic field.
  • Fast Sampling: Better coverage at faster speeds.
  • Very Low Heading Error: Get very clean, repeatable measurements without fear of instrument noise impacting the data.
  • Low AC Field Interference: Survey next to power lines when necessary.
  • Rugged and Reliable: Weatherproof. Survives three-foot drop onto hard surface.
  • Ultra-stable: No need to calibrate sensors.
  • Export Version Available: Use anywhere in the world without need for an export license (except embargoed countries). See specifications.

Technical Details

G-823A Magnetometer Specification List

G-823A Magnetometer

  • Operating Principle: Self-oscillating split-beam Cesium Vapor (non-radioactive)
  • Operating Range: 20,000 to 100,000 nT
  • Operating Zones: The earth’s field vector should be at an angle greater than 10° from the sensor’s equator and greater than 10° away from the sensor’s long axis. Automatic hemisphere switching.
  • Sensitivity: <0.004 nT/√Hz rms. (SX (export) version: <0.02 nT/√Hzrms).
  • Max Sample Rate: 20 Hz.
  • Heading Error: ± 0.15 nT (over entire 360° polar and equatorial spin)
  • Output: Cycle of Larmor frequency = 3.498572 Hz/nT, RS-232 data at 9600 baud, concatenated data streams from up to 6 sensors.
  • Power: 24 to 32 VDC, 0.75 amp at power-on and 0.5 amp thereafter.

  • Mechanical

  • Sensor: DIA: 60 mm; L: 146 mm; Weight: 0.45 kg (2.375x 5.75 in; 16 oz.) – any orientation in 177 mm (7 in) diameter stinger.
  • Sensor Electronics: DIA: 63 mm; L: 279 mm; 1.36 kg (2.5x11 in; 48 oz)
  • Cables:
  • Sensor to electronics: Standard 2.77 m (9 ft) with connector on electronics end. Other lengths available from 0.75 m to 3.75 m (2.4 ft to 12.75 ft) at 1 m (40-in) increments. Lengths approximate due to cable variations.
  • Electronics to Junction Box: RS-232 to Computer, standard 8 m, 60 m max (26.26 ft, 196.85 ft max). Larmor to external counter with coupler over Coax, standard 10m, 50m max (32.81 ft, 164.04 ft max).

  • Environmental

  • Operating Temperature: -30°F to +122°F (-35°C to +50°C)
  • Storage Temperature: -48°F to +158°F (-45°C to +70°C)
  • Altitude: Up to 30,000 ft. (9,000 m)
  • Weatherproof: O-Ring sealed for operation in rain and/or 100% humidity.
  • Gradient Tolerance: 500 nT/in.
  • Temperature Drift: <0.05 nT/°C

  • Accessories

  • Standard: Power/RS-232 multi-conductor cable (electronics to power/data junction box with 9 pin RS-232 connector and power lugs), lengths to be specified, spare O-Rings, operation manual and carrying case.
  • Optional:
  • Logging Software: MagLog (Logs GPS and Mag, shows track plot, mag profile, other data).
  • Accessories: Birds, Stingers, Wingtips, Avionics, GPS, Gamma Ray, Logging Computer

  • Other Models

  • G-823B: Enjoys all of the same specifications and performance as the G-823A, with the exception of a confirmed/tested heading error specification.
  • G-823AWL: The Larmor output capability is removed for installations that don’t utilize an external counter. “B” version also available in this model.
  • G-823AWL-SX: The SX designates that this model is our “Special Export” version which has a reduced sensitivity specification of 0.02 nt/√Hzrms. This model does not require an export license prior to shipping.
G-823A Magnetometer Shipping Weights & DIMS

Shipping Weights & DIMS

Contents Dimensions (L x W x H) Weight
Case 1 - G-823A Magnetometer 20in x 20in x 21in
51cm x 51cm x 53cm


  • In-Accessible Terrain: Difficult or dangerous terrain is no longer a problem, making it perfect for surveying wetlands, heavily vegetated areas, extreme terrain, or protected lands.
  • Environmental: Find abandoned wells, pipes, and storage tanks quickly and with precise positioning.
  • Archaeology: Survey vast distances and leave potential archaeology sites undisturbed from the air.
  • Geology: Survey for regional variations in the magnetic field.
  • UXO Detection: Collect data at high speed with a fast sample rate, making detection and delineation of UXO quick and easy.