Gauss meters measure the strength of magnetic fields. While some only measure the magnitude of the field, others also measure the direction. Applications range from locating shipwrecks to measuring solar wind.
In 1833, Carl Friedrich Gauss, invented the first instrument to measure magnetic fields. His early magnetometer consisted of a bar magnet suspended in midair by a string. While it indicated the direction of the magnetic field, it offered only a crude measure of the strength.
Modern Gauss Meters
The modern Gauss meter comes in two varieties; scalar meters, which measure just magnitude at a given point, and vector meters, which also indicate the direction of the field. Three scalar meters can be aligned to make a vector Gauss meter.
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Hall Effect Meters
The most common Gauss meter relies on the Hall effect, which is a measurable voltage that is produced when a magnetic field crosses an electrical current. If the current remains the same, then a small change in the magnetic field produces a similar and predictable change in the voltage.
Another common Gauss meter, known as the fluxgate meter, measures the magnetic field along a given direction. Its main mechanism is two current loops coupled through induction. When an alternating current is fed into the first coil, it generates a magnetic field that produces an equal but opposite current in the other coil. However, in the presence of an external magnetic field, the current induced in the second loop will differ from the input current in a way that is predictable. Multiple fluxgate meters can be used to determine directionality.
The proton precession magnetometer, or the proton Gauss meter, uses nuclear magnetic resonance--the tendency of atoms to absorb and then emit magnetic and electromagnetic energy. The strength of the magnetic field can be measured by the frequency of the atomic excitation. The proton Gauss meter is one of the most accurate means of measuring a magnetic field.