Wheatstone bridge

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Wheatstone bridge

A device used to measure the electrical resistance of an unknown resistor by comparing it with a known standard resistance. This method was first described by S. H. Christie in 1833. Since 1843 when Sir Charles Wheatstone called attention to Christie's work, Wheatstone's name has been associated with this network.

The Wheatstone bridge network consists of four resistors RAB, RBC, RCD, and RAD interconnected as shown in the illustration to form the bridge. A detector G, having an internal resistance RG, is connected between the B and D bridge points; and a power supply, having an open-circuit voltage E and internal resistance RB, is connected between the A and C bridge points. See Bridge circuit

Wheatstone bridge circuitenlarge picture
Wheatstone bridge circuit

If the network is adjusted so that Eq. (1) is satisfied, the

(1) 
detector current will be zero and this adjustment will be independent of the supply voltage, the supply resistance, and the detector resistance. Thus, when the bridge is balanced, Eq. (2)
(2) 
holds, and, if it is assumed that the unknown resistance is the one in the CD arm of the bridge, then it is given by Eq. (3). (3)  See Resistance measurement

Wheatstone bridge

[′wēt‚stōn ′brij]
(electricity)
A four-arm bridge circuit, all arms of which are predominately resistive; used to measure the electrical resistance of an unknown resistor by comparing it with a known standard resistance. Also known as resistance bridge; Wheatstone network.