 # Hay’s bridge for measurement of inductance

## Hay’s bridge for measurement of inductance :

The Hay’s bridge is modification of the Maxwell’s bridge. The connection diagram of the Hay’s bridge is shown in figure below. This Hay's bridge uses a resistor in series with a standard capacitor (unlike the Maxwell’s bridge which uses a resistance in parallel with the capacitor). Hay's bridge for measurement of inductance

Let

L1=unknown resistance having a resistance R1,

R2, R3, R4=known non-inductive resistance,

C4=standard capacitor.

At balance, Separating real and imaginary term, we obtain: Solving the above two equations we have, The Q factor of the coil is : ### Advantages of the Hay’s bridge:

1)      This bridge gives very simple expression for unknown inductance for high Q coils, and is suitable for coils having Q > 10.

2)      This bridge also gives the simple expression for Q factor.

3)      From expression of Q factor it is clear that for high Q factor the value of resistance R4 should be small.