Dictionary of Electrical Engineering

Commonly used terms in the Electrical industry.

Wheatstone bridge
a bridge circuit where all arms are resistors. The condition of balance in the circuit is used for precise measurement of resisors. In this case, one of the arms is an unknown resistor, another arm is a standard resistor (usually a variable resistor box), and two other arms (called ratio arms) are variable resistors with a well determined ratio. When the condition of balance is achieved, one can calculate the unknown resistor multiplying the standard resistor value by the ratio of ratio arms resistors. The precision of measurements is 0.05% for the range 10 ohms to 1 megohm.

The Wheatstone bridge is used for resistor measurements at DC and AC (in the universal impedance bridges).

Moreover, the Wheatstone bridge is widely used in resistive transducers where one or more arms is substituted by resistors
the resistance of which depends on a physical variable (temperature, pressure, force, etc.). In these applications, the deflection from balance is used for measurement of the physical variable.