Definition
A precision low-resistance resistor connected in parallel with an ammeter to extend its current-measuring range. Most of the circuit current flows through the shunt, while a small, known fraction flows through the meter movement. The meter's scale is calibrated to display the total current.
Plain English
A small resistor placed beside an ammeter so that most of the electrical current bypasses the meter. The meter only senses a tiny share of the current but is marked to show the full amount, which lets a delicate meter measure large currents safely.
Context Anchor
Seen in aircraft electrical instrument discussions, especially with ammeters and other meters that measure current.
Derivation
From the English word 'shunt,' meaning to turn aside or divert onto a side path. The term came from railway use, where a shunt diverted a train onto a side track. In electrical work, the shunt diverts most of the current around the meter.
Why Pilots Care
Enables accurate, continuous monitoring of battery and alternator current without risking damage to the instrument, helping detect electrical problems before they affect flight.
Analogy
It is like a bypass lane around a narrow bridge. Most traffic takes the bypass, while just enough goes over the bridge to show how much total traffic is moving.
Intuition Check
A shunt is not the instrument itself. It is the controlled bypass path that helps the instrument measure current safely.
Example Sentence 1
The technician traced the unsteady ammeter reading to a loose connection at the instrument shunt behind the firewall.
Example Sentence 2
Before takeoff the pilot confirmed the ammeter reading was reliable because the instrument shunt was properly sized for the aircraft's electrical load.