Plain English Meaning
A small electronic sensor that detects which way the Earth's magnetic field is pointing, so the aircraft's instruments can show an accurate magnetic heading.
Full Definition
An instrument that measures the strength and direction of a magnetic field. In modern aircraft, a magnetometer senses the Earth's magnetic field and sends that data electronically to the heading system, which displays magnetic heading on the cockpit instruments.
Context Anchor
Seen in compass-turn and heading-system discussions, especially when an aircraft uses an electronic heading display instead of only a simple magnetic compass.
Derivation
From the Greek 'magnes' (magnet) and 'metron' (measure). Literally a 'magnet measurer' -- a device built to measure magnetic fields rather than just point along one like a simple compass needle.
Why Pilots Care
Supplies reliable heading information to the attitude and heading reference system, allowing accurate turns and navigation when the wet compass is unusable.
Intuition Check
A magnetometer is not the compass display itself. It is the sensor that detects Earth’s magnetic field and helps the display show a magnetic heading.
Example Sentence 1
The magnetometer, mounted in the wingtip away from electrical interference, sends magnetic heading data to the primary flight display.
Example Sentence 2
Modern glass cockpits replace the traditional compass with data from the magnetometer for smoother instrument flight.