# Owen’s Bridge – Phasor diagram & Advantages

Owen’s bridge is an AC bridge used for measurement of inductance of a coil in terms of capacitance. It is used for low Q-coils. Owen’s bridge is shown in figure 1 under balance condition.

Contents

From figure 1, there are four arms as

arm 1 = ab

arm 2 = ad

arm 3 = bc

arm 4 = dc

where

L1 is an unknown self-inductance of resistance R1
R2 is a variable non-inductive resistance
R3 is a fixed non-inductive resistance
C2 is a variable standard capacitor
C4 is a fixed standard capacitor

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

At balance condition,

Z1Z4 = Z2Z3

On comparing real and imaginary part both side, we have

## Advantages of Owen’s Bridge

1. The equations obtained are simple.

2. These equations do not contain any frequency part.

3. Wide range of inductance can be measured with this bridge.

## Disadvantages of Owen’s Bridge

1. The variable capacitor, C2 used is costly and has less accuracy.

2. The variable capacitor, Cvalue becomes large while measuring inductance for a high Q-coils.

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