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WIEN'S BRIDGE
The Wien bridge is a type of bridge circuit that was developed by Max Wien in 1891. The bridge consists of four resistors and two capacitors. At the time of the Wien bridge's invention, bridge circuits were a common way of measuring component values by comparing them to known values.
FUNCTION
The bridge is used for frequency measurement.
FEATURE
Also used for measurement of an unknown capacitance with great accuracy
The impedance of one arm is:
Z1 = R1- j/ωC1
The admittance of the parallel arm is:
Y3 = 1/R3 + jωC3
Using the bridge balance equation:
we have, Z1Z4 = Z2Z3
Therefore, Z1Z4 = Z2/Y3,ie. Z2 = Z1Z4Y3
R2 = R4 ( R4 - j/ωC1 ) ( 1/R3+jωC3 )
R2 = (R1(R4)/R3) - (jR4/ωC1R3) + jωC3R1R4 + (C3R4/C1)
R2 = (R1R4/R3 + CR3R4/C1) - j(R4/ωC1R3 - ωC3R1R4)
Equating the real and imaginary terms we have
R2/R4 = (R1/R3) - (C3/C1)
C3 = 1/(ω2 C1R1R3)
f = 1/2π(C1C3R1R3)1/2
Video for further understanding
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