Bridge circuit

Bridge Circuit

A bridge circuit is an electrical circuit configuration that is designed to measure an unknown electrical resistance by balancing two legs of a bridge circuit, one leg of which includes the unknown component. The primary benefit of a bridge circuit is its ability to provide extremely accurate measurements (in contrast to voltage or current measurement methods), which is why it is commonly used in high-precision applications such as laboratory-grade test equipment.

Principle of Operation

The basic idea of a bridge circuit is to create two parallel branches of a circuit and adjust the parameters in one branch until the total resistance, or impedance, in both branches is equal. This is known as "balancing" the bridge. The unknown resistance is then calculated from the known resistances and the balance condition.

Types of Bridge Circuits

There are several types of bridge circuits, each with its own specific applications and advantages. Some of the most common types include the Wheatstone bridge, the Kelvin bridge, and the Maxwell bridge.

Wheatstone Bridge

The Wheatstone bridge is the most common type of bridge circuit. It is named after Sir Charles Wheatstone, who popularized its use in the mid-19th century. The Wheatstone bridge is used to measure an unknown electrical resistance.

Kelvin Bridge

The Kelvin bridge, also known as the Kelvin double bridge and the Thompson bridge, is a modification of the Wheatstone bridge used for measuring very low resistances.

Maxwell Bridge

The Maxwell bridge is a modification of the Wheatstone bridge used for measuring the inductive reactance of a circuit component.

Applications

Bridge circuits are used in a wide variety of applications, including electrical measurement, control systems, and communication systems. They are particularly useful in situations where high precision is required.

See Also

• Ohm's law
• Electrical impedance
• Electrical resistance and conductance