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SCHERING'S BRIDGE
SCHERING'S BRIDGE
The Schering bridge use for measuring the capacitance of the capacitor, dissipation factor, properties of an insulator, capacitor bushing, insulating oil and other insulating materials. It is one of the most commonly used AC bridge. The Schering bridge works on the principle of balancing the load on its arm.
Let, C1 – capacitor whose capacitance is to be determined,
R1 – a series resistance, representing the loss of the capacitor C1.
C2 – a standard capacitor (The term standard capacitor means the capacitor is free from loss)
R3 – a non-inductive resistance
C4 – a variable capacitor.
R4 – a variable non-inductive resistance parallel with variable capacitor C4.
When the bridge is in the balanced condition, zero current passes through the detector, which shows that the potential across the detector is zero. At balance condition
Z1/Z2 = Z3/Z4
Z1Z4 = Z2Z3
So,
Equating the real and imaginary equations, we get,
The equation (1) and (2) are the balanced equation, and it is free from the frequency.
Advantages of Schering Bridge
The following are the advantages of the Schering bridge.
1. Balance equations are free from frequency.
2. The arrangement of the bridge is less costly as compared to the other bridges.
Dissipation Factor
Dissipation factor of series R-C tell about the quality of capacitor or how close the phase angle of the capacitor to the ideal value 90̊
D = ωCxRX
And also
Q = 1/D
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