Q. Briefly explain about Wheatstone Bridge?

Null measurements are made with bridge circuits and related configurations. They differ from direct measurements in that the quantity being measured is compared with a known reference quantity. The balancing strategy avoids undesirable interaction effects and generally results in more accurate measurement than the direct one.

By far the most common is the Wheatstone bridge designed for precise measurement of resistance. Figure 1.4.2 shows the basic circuit inwhich themeasurement of an unknown resistance Rx is performed by balancing the variable resistances Ra and Rb until no current flows through meter A. Under this null condition,

where Rs is the known standard resistance. There are other bridge-circuit configurations to measure inductance and capacitance. Typical instruments utilizing bridge circuits are found in strain gauges measuring stress and in temperature measuring systems with thermocouples and thermistors.