Rugged Overhauser Magnetometer

GEM offers a range of magnetometers and gradiometers based on Proton Precession,
Overhauser, and Potassium methods. The Overhauser system is a revolutionary instrument developed by GEM to offer a rugged, low power and sensitive alternative to Proton Precession and some other alkali vapour magnetometers.

The Overhauser system is a super-charged Proton magnetometer that uses a special mixture for energization and measurement. Overhauser offers a number of significant benefits over Proton and some alkali vapour systems.

GEM’s GSM-19 (Overhauser) magnetometer is a primary standard in mineral exploration and magnetic observatories. As a standard for magnetic observatories, this system has proven itself – for its high sensitivity, absolute accuracy and dependability. Overhauser is also used in archaeology, pipeline mapping, and other engineering and environmental applications.

Overhauser Benefits

The GSM-19 is designed to be a mid-range instrument with excellent benefits for subsurface exploration. As a mid-range instrument, the Overhauser system offers an order-of-magnitude increase in sensitivity over GEM’s Proton system and matching sensitivities of some alkali devices. Overhauser Magnetometers provide high efficiency and sensitivity, which is comparable to a cesium magnetometer.

But the benefits do not end there. Overhauser also provides high absolute accuracy, ruggedness, and reliability – numerous systems are in operation around the world with an excellent performance record so that the GSM-19 can be counted on in any situation. Early versions of the Overhauser, developed in 1983, are still running on a continuous basis at an observatory in Japan.

GEM Overhauser Magnetometer
GEM Overhauser magnetometer with GPS button (top),
sensor filled with a special mixture called a free radical,
console, and backpack. The system is extremely light
and robust – making it an ideal choice for many
subsurface investigations.

Overhauser also offers the option of pulsed versus continuous operation. With pulsed operation, the system provides an energizing pulse to initiate the reading. With continuous operation, the system is always active – so that data can be recorded at any time and anywhere conveniently.

GEM’s Overhauser magnetometer/gradiometer also offers much less power consumption than Proton or alkali vapour systems so you can perform a whole day’s work on a single charge. Other benefits include an omnidirectional sensor (i.e. no dead zones) and fast sampling. Fast sampling of up to 5 Hz is available – an important capability for many larger surveys that may be of interest. Fast sampling gives the option
to automate readings on a vehicle such as an all-terrain-vehicle (ATV), snowmobile sled, etc.

The Overhauser also does not require maintenance – it is as robust and effective an instrument as ever made for the field. It also has superior environmental specifications including operating temperatures of -55°C to +50°C – giving unparalleled performance throughout.

The GSM-19 is perhaps the world’s most robust magnetic instrument, based on its ongoing development that continues to this day. In fact, the system is almost unbreakable as our clients continue to prove in their daily work. The mechanics of the sensor and console have been ruggedized from previous versions while maintaining environmental specifications and weatherproof characteristics.

Moreover, the cables and connectors have been carefully selected for maximum stability and performance. An improved backpack gives handsfree operation while ensuring a stable, lightweight platform for making measurements. All considered, this is an excellent product from an experienced instrumentation provider.

Integrated GPS

Integrated GPS is a huge development. Led by GEM, the GSM-19 has been at the forefront of GPS technology development. This gives highly accurate time for base station corrections as well as other capabilities, such as Waypoint Programming.

Walking VLF is also available in combination with an Overhauser magnetometer. For more information, please see the Airborne and Ground VLF brochure from GEM.

With Waypoints, you design your survey on your personal computer and import the stations with ease into the magnetometer console. Then, the system will guide you to each Waypoint where a reading is to be made. With Walking mode, you have a nearly continuous record of GPS-referenced datapoints – a major advantage in surveying because you save time in the field and it eliminates the possibility of positioning mistakes.


Sensitivity: 0.022 nT @ 1 Hz, (0.015 nT option)
Resolution: 0.01 nT
Absolute Accuracy: +/- 0.1 nT
Dynamic Range: 20,000 to 120,000 nT
Gradient Tolerance: Over 10,000 nT/m
Sampling Intervals: 60+, 5, 3, 2, 1, 0.5, 0.2 sec
Operating Temperature: -55°C to +50°C

View Brochure

To learn more about the Overhauser system or to obtain complete specifications, contact GEM. Our World is Magnetic!



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