Definition
An electrical test instrument that measures the current flowing through a wire by clamping a hinged jaw around the wire without cutting it or disconnecting it. The jaws act as a sensor that detects the magnetic field produced by the current, and the instrument converts that field into a current reading on its display.
Plain English
A meter with a set of jaws that open and close like a clothes peg. You squeeze it open, place it around a wire, and it tells you how much electrical current is flowing through that wire — without you having to cut or unplug anything.
Context Anchor
Seen during aircraft electrical system troubleshooting, especially when a mechanic needs to check current draw in a wire while the system remains connected.
Derivation
The name describes the tool plainly: it clamps onto a wire, and an ammeter measures amperes (the unit of electrical current). 'Ammeter' is a shortening of 'ampere meter,' named after André-Marie Ampère, the French physicist who studied electric current in the early 1800s.
Why Pilots Care
Allows safe measurement of current without interrupting power, critical for diagnosing issues like excessive draw in avionics or lighting systems.
Grounding Statement
The tool senses the magnetic effect created by current flowing through one wire.
Intuition Check
A clamp-on ammeter does not measure by touching bare wire. It clamps around one conductor and reads the current flowing through it.
Example Sentence 1
The technician used a clamp-on ammeter around the starter cable to confirm the motor was drawing the correct current during engine start.
Example Sentence 2
Using a clamp-on ammeter confirmed that the starter motor was drawing the expected amperage during engine start.