Definition
Magnetometers are sensors that measure the strength and direction of the Earth's magnetic field. In an Attitude and Heading Reference System (AHRS), they provide the magnetic heading reference that allows the system to display the aircraft's heading on electronic flight instruments.
Plain English
Small electronic sensors that detect which way is magnetic north, so the aircraft's instruments can show an accurate heading.
Context Anchor
Seen in discussions of attitude and heading reference systems, especially where the system gets its heading information.
Derivation
From Greek 'magnes' (magnet) and 'metron' (measure). Literally 'magnet measurer' — a device that measures magnetic fields. The name tells you exactly what it does.
Why Pilots Care
Supplies reliable magnetic heading data to the AHRS even when GPS or other navigation sources are unavailable or unreliable.
Intuition Check
Do not confuse magnetometers with magnetos. Magnetometers sense the Earth's magnetic field; magnetos create electrical power for engine ignition.
Example Sentence 1
The AHRS uses a magnetometer mounted in the wingtip to sense the Earth's magnetic field and display heading on the primary flight display.
Example Sentence 2
After maintenance the pilot performed a compass swing to ensure the magnetometers remained properly aligned.