* Maxwell inductance bridge is an AC bridge used* for

*measurement of inductance*

*of a coil by comparison with a variable standard self-inductance.*Maxwell inductance bridge is shown in figure 1 under balance condition. Under balance condition, the current (I

_{d}) through the detector is zero. Hence current through arm ab and arm cd is the same. The current through arm ad and arm dc is the same.

**Contents**show

From figure 1, there are four arms as

arm 1 = ab

arm 2 = ad

arm 3 = bc

arm 4 = dc

where

L_{1} is an *unknown self-inductance* of resistance R_{1}

R_{2} is a variable non-inductive resistance

L_{2} is a variable inductance

R_{3} is a fixed resistance

R_{4} is a fixed resistance

Therefore, the impedances of arms 1, 2, 3 and 4 are respectively,

Z_{1} =

Z_{2} =

Z_{3} = R_{3}

Z_{4} = R_{4}

At balance condition,

Z_{1}Z_{4} = Z_{2}Z_{3}

On comparing real and imaginary part both side, we have

and

## Phasor Diagram of Maxwell inductance Bridge

## Advantages

1. The bridge balancing is simple.

2. These equations do not contain any frequency part.

3. This circuit is cheap.