Anderson Bridge Explained

 

Anderson Bridge

What is Anderson Bridge?

The Anderson Bridge is an AC bridge circuit used to measure the self-inductance of a coil with high accuracy. It is a modified version of the Maxwell Bridge, using an additional capacitor for improved precision.

• Used to measure unknown inductance (L)
• Includes resistors, a standard capacitor, and an unknown inductor
• Works on the bridge balance principle

Key Idea

At balance condition, the impedance of one arm equals the impedance of the opposite arm, resulting in no current through the detector.

Mathematical Formula

L = C × R₂ × (R₃ + R₄ + (R₃ × R₄) / R₅)

Where:

• L = Inductance of the coil
• C = Standard capacitor
• R₂, R₃, R₄, R₅ = Known resistances

Important Notes

• The formula is derived using Kirchhoff’s laws and AC impedance balance
• More accurate than many other bridge methods
• Uses a fixed capacitor instead of a variable inductor

Advantages

• High accuracy
• Uses a standard capacitor
• Suitable for low inductance measurement

Disadvantages

• More complex circuit
• Requires more calculations

The Anderson Bridge works like a balancing system. When the bridge is balanced, the unknown inductance can be calculated using known resistor and capacitor values.