The Wheatstone bridge consists of four resistors connected in a square circuit. For the classic application of resistance measurement, three of the four resistors are variable resistors of known values. The fourth resistor is unknown. If a bridge voltage is applied from a to c, then the electric current flowing through the bridge is split, flowing through R1 and R2 on one side, and R4 and R3 on the other side. If a voltmeter is connected from b to d, then by adjusting the three known variable resistors until the voltmeter reads zero the bridge can be "balanced" with equal currents flowing through both arms of the bridge. In a balanced bridge the unknown resistance can then be calculated from the values of the known resistances.
In a modification of this application, bridge circuits are frequently used to provide an amplified, highly sensitive output from transducers, by using such transducers as one or more elements of a bridge.
Related categories• ELECTRICITY AND MAGNETISM
• LABORATORY EQUIPMENT
Home • About • Copyright © The Worlds of David Darling • Encyclopedia of Alternative Energy • Contact