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Wein bridge

 Wein bridge

Basically, the bridge is used for the frequency measurement but it is also used for the measurement of the unknown capacitor with great accuracy.
Its one ratio arm consists of a series RC circuit i.e. R1 and C1. The second ratio arm consists of a resistance R2. The third arm consists of. the parallel combination of resistance and capacitor i.e. R3 and C3.




Application:

1. The bridge is used to measure the frequency in the audio range. The audio range is [20-200 - 2 k - 20 k] Hz.
2. The resistances are used for the range changing while the capacitors are used for fine frequency control.
3. The bridge can be used for capacitance measurement if the operating frequency is known.
4. The bridge is also used in a harmonic distortion analyzer, as a notch filter and in audio frequency and radio frequency oscillators as a frequency-determining element. 
5. This bridge can readily obtain an accuracy of 0.5 % - 1 %.

Advantage:

1. The Wien bridge can be used to determine unknown frequencies where the device can be calibrated in terms of frequency which can control the balance condition of the bridge.
2. The bridge can be effectively used for the frequency measurement in between 100Hz to 100 kHz range. In most of the practical Wien bridges the accuracy of 0.1 % to 0.5 % can be achieved.
3. In some special purpose applications, the Wien bridge can also be used to determine value of unknown capacitance.

Disadvantage:

1. As the Wien bridge is frequency sensitive, it is difficult to balance it.
2. It requires purely sinusoidal voltage at its input terminals. If the input voltage consists of harmonics, then the true balance point gets masked and the harmonics in the input voltage produce the output voltage.



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