Definition
An electrical test instrument used to measure resistance in an electrical circuit or component, expressed in ohms. The ohmmeter applies a small known voltage from an internal battery, measures the resulting current flow, and displays the resistance value, typically with the circuit de-energized.
Plain English
A handheld tool that tells you how hard it is for electricity to flow through a wire or part. The reading is in units called ohms — a low number means electricity flows easily, a high number means it doesn't.
Context Anchor
Seen in aircraft electrical maintenance, inspection, and troubleshooting when checking wiring, switches, lights, motors, and other electrical parts.
Derivation
Named after Georg Ohm, the German physicist who described the relationship between voltage, current, and resistance. 'Meter' comes from the Greek 'metron,' meaning 'measure.' So an ohmmeter is literally a 'measurer of ohms.'
Why Pilots Care
Mechanics use ohmmeters constantly when chasing electrical faults. A reading of zero ohms confirms a wire is intact (continuity); a very high or infinite reading confirms an open circuit or broken connection. Misreading these values can lead to incorrect troubleshooting and unresolved faults.
Intuition Check
An ohmmeter is not the same as a voltage tester. It checks resistance, and it is normally used only when the circuit power is off.
Example Sentence 1
The technician used an ohmmeter to verify continuity through the navigation light wiring before reinstalling the wing tip.
Example Sentence 2
Before installing the new battery, check the ground cable with an ohmmeter to confirm low resistance.