How do magnetometers work?

Magnetometers are instruments used to measure the changes, strength, and direction of a magnetic field. They exist as everyday objects like a compass, iPhones, aircraft, and metal detectors, and there are several types of magnetometers depending on the type of measurements needed.

Magnetometers are able to detect ferromagnetic materials, direction and amplitude of magnetic fields, and a magnetometer measures the magnetic field at the exact point of it’s location. Since the Earth’s magnetic field, (undisturbed) should be at equilibrium, a magnetometer would be able to detect when the magnetic field at some point is unsettled.

Types of magnetometers

There are several types of magnetometers for various uses, and they fall into two different categories: scalar or vector. Scalar magnetometers measure the total strength of a magnetic field, while vector magnetometers measure both strength and direction.

A fluxgate magnetometer is constructed by wrapping coils of wire around a ferromagnetic material, like a bar of iron and applying an AC (alternating current) through the bar. The bar and the wrapped coil will create a magnetic field. By wrapping the wire in opposite directions on each bar, the current direction will also move in two opposing directions.

Reversing the current in the wire causes the magnetic field to also reverse. Because of this, the magnetic fields cancel each other out, which then allows for external magnetic fields to be measured since any disturbance that happens in the “canceled,” magnetic field of the fluxgate magnetometer. 

To measure geomagnetic activity, the GOES-16 spacecraft utilizes two tri-axis fluxgate magnetometers monitoring three orthogonal (right-angled) components of the geomagnetic field at geosynchronous (rotation that is synchronous with Earth’s rotation) orbit with a sampling rate of 10 Hz.