Different types of magnetometer and guasssmeters | applied electronics engineering


Different types of magnetometer and guasssmeters

By Applied Electronics - Saturday, April 1, 2017 No Comments
Magnetometers and Gaussmeters are used to measure magnetic field strength. In the world of instrumentation, it is conventional to refer to devices that measures low magnetic field(<1mT) as Magnetometer and those devices that measures high magnetic field(>1mT) as Gaussmeters.

Below is a chart of classification of Magnetometer and Gaussmeters.

As you see in the chart the Magnetometers can be further divided into vector and scaler Magnetometers. Vector Magnetometer measure both the strength of the field and the direction whereas scalar Magnetometer only measures the magnitude of the field strength and does not measure the direction of the field.

Most widely used magnetometers are the Search Coil(Induction Coil) and fluxgate magnetometer. They are widely used for measuring direction of the field as well as measuring field strength. The search coil although is depicted as measuring low magnetic field, it can as well measure high magnetic field. It can be classified as gaussmeter.

The fiber optic magnetometer is relatively recently developed and used for low-field measurement. It has approximately the same sensitivity as a fluxgate magnetometer but has for better performance.  The SQUID(Superconducting Quantum Interference Device) magnetometers is the most sensitive magnetic field sensor among all the magnetometers/gaussmeters. Such sensors operate at temperatures near absolute zero and require special thermal control systems. This makes the SQUID based magnetometer more expensive, less rugged, and less reliable.

The Hall effect device is the oldest and most common high-field vector sensor used in gaussmeters. It is especially useful for measuring extremely high fields (>1 T). The magnetoresistive sensors cover the middle ground between the low- and high-field sensors. Anisotropic magnetoresistors (AMR) are currently being used in many applications, including magnetometers. The recent discovery of the giant magnetoresistive (GMR) effect, with its tenfold improvement in sensitivity, promises to be a good competitor for the traditional fluxgate magnetometer in medium-sensitivity applications. The proton (nuclear) precession magnetometer is the most popular instrument for measuring the scalar magnetic field strength. Its major applications are in geological exploration and aerial mapping of the geomagnetic field. Since its operating principle is based on fundamental atomic constants, it is also used as the primary standard for calibrating magnetometers. The proton precession magnetometer has a very low sampling rate, on the order of 1 to 3 samples per second, so it cannot measure fast changes in the magnetic field. The optically pumped magnetometer operates at a higher sampling rate and is capable of higher sensitivities than the proton precession magnetometer, but it is more expensive and not as rugged and reliable.

 See Wiley Survey of Instrumentation and Measurement PDF free download.


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