G-822A Cesium Magnetometer

The G-822A is designed for all airborne or mobile applications where the unique combination of high sensitivity and very rapid sampling of the earth’s magnetic field are required. Applications include mapping geologic structure for mining, oil and gas exploration and the detection and delineation of target bodies in environmental, archaeological or military UXO ordinance type surveys. The unit consists of a high performance low heading error cesium vapor sensor with its associated cables and driver electronics Optional internal counter available.

The G-822A sensor uses a precise well-proven design with carefully selected and tested components to insure the very best specifications in sensitivity, low noise, heading error and absolute accuracy. A proven record of stable and reliable operation over long periods is the
hallmark of the industry standard G-822A. A single coaxial cable of up to standard 10 meters length supplies both 28 VDC power and Larmor signal transmission from the sensor driver electronics to a RMS Instruments’ AARC500 Automatic Digital Compensator, Geometrics 822A Super-Counter or customer supplied Larmor counter. Internal or external signal/power filter-decoupler assemblies are available to provide extremely low noise operation.

The interconnect cable from the driver/electronics to the sensor may be supplied in various lengths with a standard length of 13.5 ft. Tuning throughout the earth’s field range is fully automatic and includes automatic hemisphere switching for equatorial surveys.

The sensor/electronics package is weatherproof, temperature controlled, and delivers full performance under extreme operating conditions. Accessories include special mounting clamps and orientation platforms for installation into a variety of vehicle or aircraft mounting configurations, as well as Birds, Stingers, Wing Tip fairings and complete integrated airborne geophysical survey systems with data logging and display.
 Features:

     Airborne and Vehicle Applications with Multi- Sensor Array Capability

     Automatic Hemisphere Switching

     Highest Sensitivity – 0.0005 nT/√Hz RMS with the G-822A Super-Counter

     Highest Versatility – Full Aircraft Compensation with RMS AARC500. Super-Counter option for post acquisition compensation or optional G- 823A configuration with CM-221 Internal Mini- Counter

     Very low heading error – ±0.15nT over entire 360< Equatorial and Polar spins

     Gradiometer arrays offering simultaneous operation of up to four separate sensors with the RMS Instruments AARC500, Geometrics’ G-822A Super-Counter or optional CM-221 Internal Minicounter (up to 8 sensors)

     Geometrics offers complete turnkey systems including Birds, Stingers, Wingtip installation accessories as well as Digital Data Acquisition Systems, Flight Path Recovery, GPS Navigation, Gamma Ray pectrometers, VLF EM , Post Acquisition Data Processing Software and Training
 Specifications:
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 6° from the sensor’s equator and greater than 6° away from the sensor’s long axis. Automatic hemisphere switching.
SENSITIVITY:

<0.0005 nT/√Hz rms. Typically 0.003 nT P-P at a 0.1 second sample rate using 822A Supercounter, 0.02nT P-P for CM-221
HEADING ERROR:

±0.15 nT (over entire 360° polar and equatorial spin)
ABSOLUTE ACCURACY:

<3 nT throughout range
OUTPUT:

Cycle of Larmor frequency = 3.498572 Hz/nT, 2V P-P coupled through the sensor power input
MECHANICAL:
Sensor:

2.375” (60.32 mm) dia., 5.75” (146 mm) long, 12 oz (339 g) - any orientation in 7” dia. stinger
Sensor Electronics:

2.5” (63.5 mm) dia., 11” (279.4 mm) long, 22 oz (623 g)
Cables:

Sensor to electronics:

Standard 162 in. (13 ft 6 inch or4.1 m). Other lengths available from 2.4ft (0.75m) at 40 inch (1m) increments with connector on electronics end. Note: Cable lengths are approximate due to cable dielectric variations

Sensor Electronics to Counter:

 Standard 10m, up to 165 ft (50 m) (Coax with signal superimposed on power, requires decoupler board or box.)
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 or 100% humidity
POWER: 24 to 32 VDC, 1 amp at turn-on and 0.5 amp thereafter
ACCESSORIES:
Standard:
Power/Larm or coaxial cable (electronics to counter), standard length 10m, maximum 50m, spare O rings, operation manual and carrying/storage case
Optional:
Signal/Power Decoupler, board or multichannel
box:
Separates the Larmor signal from the power (28 V) to enable connection to RMS Instruments’ AADCII A utomatic Aeromagnetic Compensator or Customer supplied counter

Internal Decoupler:

 P/N 27504 - up to two sensor installation

External Decoupler:

P/N 27560 - three and four sensor installation
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