BEKG 1233 Instrumentation and Measurement

6.2 MAXWELL'S BRIDGE

MAXWELL'S BRIDGE

The Maxwell bridge is a bridge that is used to determine a circuit's self-inductance.

A more sophisticated version of the Wheatstone Bridge is the Wheatstone Bridge.

The Maxwell bridge is based on the comparison principle, which states that the value of an unknown inductance may be calculated by comparing it to a standard value.

Let, L₁ – unknown inductance of resistance R₁.

R₁ – Variable inductance of fixed resistance r₁.

R₂, R₃, R₄ – variable resistance connected in series with inductor L₂.

C₄ – known non-inductance resistance

For balance condition,

By separating the real and imaginary equation we get,

The above equation shows that the bridges have two variables R₄ and C₄ which appear in one of the two equations and hence both the equations are independent.

The circuit quality factor is expressed as,

Advantages of the Maxwell’s Bridges

· The balancing equation for the circuit is frequency-independent.

· The two balancing equations have nothing to do with one another.

· The Maxwell's inductor capacitance bridge is used to determine the high range inductance.

Disadvantages of the Maxwell’s Bridge

· The Maxwell inductor capacitance bridge necessitates the use of a variable capacitor, which is highly expensive. As a result, the conventional variable capacitor is used in the bridges on occasion.

· The bridge is solely used to assess average-quality coils.

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