Definition
A direct-current measuring instrument that uses a small coil of wire suspended in the field of a permanent magnet. When current flows through the coil, it produces a magnetic field that interacts with the permanent magnet, causing the coil to rotate against a calibrated spring. A pointer attached to the coil indicates the amount of current on a scale. The D'Arsonval movement is the basic mechanism inside most analog ammeters, voltmeters, and many other electrical gauges found in aircraft.
Plain English
A small needle-style electrical gauge that works by passing current through a coil sitting between magnets. The current makes the coil twist, the needle moves, and the position of the needle tells you how much current is flowing.
Context Anchor
Seen in aircraft electrical-system training, maintenance troubleshooting, and explanations of older analog cockpit or shop test instruments.
Derivation
Named after Jacques-Arsène d'Arsonval, a 19th-century French physicist who developed the moving-coil galvanometer the meter is based on. The name is a person's name, not a technical word, so it doesn't describe how the meter works -- it just identifies who designed the original mechanism.
Why Pilots Care
Delivers accurate readings of electrical system status needed to monitor battery and alternator performance in flight.
Intuition Check
Do not read D'Arsonval as a unit of measurement or a brand name. It is the name of a specific meter movement design.
Example Sentence 1
The aircraft's ammeter uses a D'Arsonval meter movement to show how much current the alternator is supplying to the battery.
Example Sentence 2
During the instrument check, the mechanic noted the smooth response of the D'Arsonval meter in the ammeter.