Definition
A four-arm electrical circuit used to measure an unknown resistance by balancing it against three known resistances. When the bridge is balanced, no current flows through the detector connected between the two midpoints, and the unknown resistance can be calculated from the ratio of the other three. In aviation instruments, the Wheatstone bridge is widely used in temperature, pressure, and strain-gauge sensing systems, where a change in the sensed quantity unbalances the bridge and produces a measurable output.
Plain English
A circuit arranged in a diamond shape with four resistors. By comparing them against each other, it can measure very small changes in one of them with high accuracy. Aircraft instruments use this trick to turn things like temperature or pressure changes into electrical signals.
Context Anchor
Seen in aircraft electrical systems, instrument sensors, and maintenance discussions involving pressure, temperature, fuel quantity, or strain-measuring circuits.
Derivation
Named after Sir Charles Wheatstone, the 19th-century English scientist who popularized the circuit (it was actually invented by Samuel Hunter Christie). 'Bridge' refers to the detector connection that 'bridges' the two midpoints of the circuit.
Why Pilots Care
Accurate resistance measurements help verify fuel quantity probes, temperature sensors, and other critical aircraft systems during maintenance.
Analogy
Think of a balance scale with two pans. When both sides hold equal weight, the pointer sits at center. Change one weight slightly, and the pointer swings — and the size of the swing tells you how much it changed.
Intuition Check
Do not picture a physical bridge. In this term, “bridge” means a balanced electrical comparison circuit.
Example Sentence 1
The cylinder head temperature gauge uses a Wheatstone bridge, with the temperature-sensing resistor forming one arm of the circuit.
Example Sentence 2
During an avionics check, the Wheatstone bridge confirmed that the sensor resistance remained within the manufacturer's specified range.