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DIVER MAG 1 MAGNETOMETER
INTRODUCTION TO MAGNETOMETERS:
Magnetometers are precision electronic instruments that measures the strength of the earth’s magnetic field. Once
the magnetometer is set up in an area, it will inform the operator of the strength of the earth’s magnetic field in that
area (in gammas). More importantly (for our application), if anything is brought into that area that alters the earth’s
magnetic field, it will change the readout of the magnetometer. For an object to alter the earth’s magnetic field, it must
be constructed of a ferromagnetic material (iron content). Any material that a magnet is attracted to will alter the
earth’s magnetic field and therefore can be detected by a magnetometer.
The earth’s magnetic field varies in intensity over the surface of the earth (see world map in shipping box). At the
poles, the field is concentrated and therefore has a high intensity. A magnetometer would read in the 61,000 gamma
area at the poles. At the equator, the field is quite weak. A magnetometer would read in the 24,000 gamma area at
the equator. In any given area of the world, the field is fairly even. If an iron object is introduced into the area, the lines
of force are disturbed. The amount of disturbance is a function of the mass of the object.
Over the past 45 years, almost every major buried wreck found was done so with a magnetometer. The metal-hulled
ships and barges are, of course, easy targets and can be detected from hundreds of feet away. The Spanish galleons
laden with gold and silver (metals not detectable by a magnetometer) were found by the magnetometer detecting the
ships’ anchors or ballast stones (magnetite was often used as ballast). One of the largest finds was a galleon off
Florida, found 45 years ago, carrying four hundred million dollars worth of gold and silver. The wreck was found with
a proton magnetometer (detected the anchor).
The DIVER MAG 1 is a fourth generation proton magnetometer from JW Fishers. It is a top performing microproces-
sor driven marine magnetometer detection system with a one gamma sensitivity. Cycle time (how often reading is
taken) is switch selectable for 2/5/ or 10 seconds. A two second cycle time gives a strong return signal and is fast
enough to detect even small iron/steel targets. The DIVER MAG 1 features a triaxial noise-cancelling sensor that
allows omnidirectional operation without heading error or dead zone. The system is fully digitized and displays it’s
output on an easy to read 5 digit LED for murky water or night operations. An audio output allows the diver to operate
the system without watching the LED readout. The DIVER MAG 1 is tunable worldwide. The system is easy to
maneuver and is operator adjustable for neutral buoyancy.
Power is supplied by an internal 12 vdc rechargeable battery which lasts for two continuous hours at the 5 second
cycle time. Extended operation is available by using optional belt mounted spare battery packs. Battery charger
operates from 120 vac (220 vac optional).
The DIVER MAG 1 was designed for underwater use, but can be used on land with the same 1 gamma sensitivity. A
land handle grip is provided for carrying the unit on land. The unit is quite heavy (35 lbs), so a small wheeled cart is
recommended for prolonged land use (use nonferrous metals in cart).
Modular construction allows easy field repair, should it ever be necessary. The DIVER MAG 1 is covered by a full TWO
YEAR WARRANTY.
EARTHS MAGNETIC
FIELD - NORMAL
EARTHS MAGNETIC
FIELD - IRON OBJECT
