A fluxgate magnetometer detects changes in the Earth’s magnetic field and is used by archaeologists, engineers, geologists, and the military to detect underground or underwater objects. It measures both the magnitude and direction of the field using two ferromagnetic cores and two coils of wire. Victor Vacquier invented it in the 1930s, and it was used during WWII to detect enemy ships. It is also used to detect unexploded ordnance and in physics research. Archaeologists use it to survey subsurface features and detect deposits of ancient material.
A fluxgate magnetometer is a type of scientific instrument used to detect changes in the earth’s magnetic field. Fluxgate magnetometers play an important role in detecting underground or underwater objects. Archaeologists, engineers, geologists and the military use or have used different types of fluxgate magnetometers.
A fluxgate magnetometer is a vector magnetometer, which means that it measures not only the magnitude but also the direction of the earth’s magnetic field. The device consists of two ferromagnetic cores surrounded by two coils of wire. When the magnetometer is active, alternating current passes through one of the coils, known as the “winding coil”, creating induced magnetic fields of different strengths and complementary directions in the cores. Changes in magnetic fields generate an electric current in the second coil, known as the ‘sensing coil’, which can then be measured. Exposure to changes in the earth’s magnetic field causes changes in the magnetic fields of the cores, leading to changes in the current in the sense coil.
Victor Vacquier invented the fluxgate magnetometer in the 1930s. Low flying aircraft carried fluxgate magnetometers during WWII. Large objects made of ferrous metals, such as submarines, cause localized variations in the Earth’s magnetic field, so the magnetometer was able to detect enemy ships.
Military use of the fluxgate magnetometer continued after World War II. Fluxgate magnetometers are particularly suitable for field work due to their durability and small size. As a result, they have become a common tool in the detection of unexploded ordnance such as bombs, artillery shells and land mines.
The military weren’t the only customers for a lightweight, portable instrument that could detect changes in the Earth’s magnetic field. After World War II, and increasingly from the 1960s onwards, archaeologists began using fluxgate magnetometers to survey subsurface features. Ferrous metals were not the only research substances archaeologists used magnetometers. Local burning alters the magnetic field of substances such as stone, earth and ceramics, allowing archaeologists to detect deposits of ancient material. The fluxgate magnetometer has become a favorite with archaeologists not only for its light weight and durability, but also for its typically low cost.
The fluxgate magnetometer is also used in physics research. These instruments are mounted on aircraft or spacecraft and used to measure changes in the magnetic field in the atmosphere. Spacecraft-mounted fluxgate magnetometers can measure the magnetic fields of planets other than Earth.
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