A Wheatstone bridge is a simple circuit arrangement used to measure an unknown resistance by balancing two legs of a bridge circuit, each containing known resistances. It consists of four resistive arms forming a diamond shape with a voltage source connected across one pair of diagonal ends and a galvanometer connected across the other pair. The galvanometer indicates zero current flow when the bridge is balanced, which occurs when the ratio of the resistances in one pair of arms equals the ratio in the other pair.
The Wheatstone bridge principle is based on the fact that when the bridge is balanced, no current flows through the galvanometer, indicating that the ratio of the resistances in one pair of arms is equal to the ratio in the other pair.
Applications of the Wheatstone bridge include:
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Resistance Measurement: The primary application of the Wheatstone bridge is to measure the resistance of an unknown resistor accurately. By adjusting the known resistances in one arm of the bridge until the galvanometer reads zero, the resistance of the unknown resistor can be calculated using the known resistances and the bridge's balance condition.
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Strain Measurement: Wheatstone bridges are widely used in strain gauge sensors to measure changes in resistance caused by mechanical strain. Strain gauge sensors are bonded to the surface of a structure, and as the structure deforms under load, the resistance of the strain gauge changes. By incorporating the strain gauge into one arm of the Wheatstone bridge and adjusting the other resistances until the bridge is balanced, the strain on the structure can be accurately measured.
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Temperature Measurement: Wheatstone bridges are also used in temperature sensors, such as resistance temperature detectors (RTDs) and thermistors, to measure changes in resistance caused by temperature variations. By incorporating the temperature-sensitive element into one arm of the Wheatstone bridge and adjusting the other resistances until the bridge is balanced, the temperature can be accurately measured.
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Pressure Measurement: Wheatstone bridges are employed in pressure sensors to measure changes in resistance caused by pressure variations. By incorporating the pressure-sensitive element into one arm of the Wheatstone bridge and adjusting the other resistances until the bridge is balanced, the pressure can be accurately measured.
Overall, the Wheatstone bridge is a versatile circuit arrangement used in various measurement applications, providing accurate and reliable measurements of resistance, strain, temperature, pressure, and other physical quantities.
