Definition
A specialized form of Wheatstone bridge electrical measuring circuit designed to accurately measure very low values of electrical resistance, typically below one ohm. It uses a second set of ratio arms to compensate for the resistance of the connecting leads and contact points, which would otherwise introduce significant error when measuring such small resistances.
Plain English
A precision electrical test circuit used to measure tiny resistances accurately. It cancels out the resistance of its own wires and connections, which would otherwise make the reading wrong.
Context Anchor
Seen in aircraft electrical maintenance when checking low-resistance wiring, connections, or components.
Derivation
Named after William Thomson, Lord Kelvin, the British physicist who developed this modification of the original Wheatstone bridge in the 19th century. 'Bridge' refers to the circuit shape, where the measuring point 'bridges' between two parallel paths.
Why Pilots Care
Low resistance problems can affect aircraft electrical reliability. A Kelvin Bridge helps maintenance personnel find small resistance changes that an ordinary meter setup might miss.
Intuition Check
Kelvin does not mean temperature here. In this term, Kelvin names a type of precision resistance-measuring bridge circuit.
Example Sentence 1
The avionics technician used a Kelvin Bridge to verify that the bonding strap between the engine and airframe had a resistance well below the maximum allowed value.
Example Sentence 2
During the annual inspection the mechanic used the Kelvin bridge to verify low-resistance paths between the engine case and airframe ground.