Hay’s Bridge

Hay’s Bridge

It is also a modification of the Maxwell-Wien Bridge and is particularly useful if the phase angle of the inductive impedance ɸm = tan-1(ωL/R) is large. The network is shown in figure 1. It is seen that, in the case, a comparatively smaller series resistance R1 is used instead of a parallel resistance (which has to be of a very large value).

Here

Z2 = R2

Z3 = R3 + jωL3; Z4 = R4

Balance condition is Z1Z3 = Z2Z4

Separating the reals and the imaginaries, we obtain

Solving these simultaneous equations, we get

The symmetry of expression should help the readers to remember the result even when branch elements are exchanged.