Construction of De Sauty Bridge

What is De Sauty Bridge?

De Sauty Bridge is an instrument used to measure the capacitance value in a circuit. It is an Alternating Current bridge. It is based on the principle of null deflection. De Sauty Bridge is the simplest method for comparing two capacitances. It consists of two variable resistors, one standard capacitance, and one unknown capacitance. It finds the value of unknown capacitance in terms of standard capacitance. The balance point in the bridge can be obtained by varying the variable resistors. However, to measure capacitors with dielectric loss, a modified version of the De Sauty Bridge should be used....

Working Principle of De Sauty Bridge

De Sauty Bridge is based on the principle of null deflection. When the bridge is in the balanced condition no current will flow through the galvanometer and the galvanometer shows no deflection, hence the name null deflection. When the potential across the galvanometer is different, current will pass through the galvanometer and the needle of the galvanometer shows deflection and we can understand that the bridge is in an unbalanced condition. We can make the bridge balanced by varying the values of the variable resistors. To obtain accurate measurements the variable components need to be adjusted very precisely. The current through the galvanometer at the balance condition is zero. According to Kirchoff’s circuital law, the voltage drop across a closed loop is zero. application of this law in the bridge circuit results in the dropping of sum of voltage through the individual arms of the loop which is 0. At balance condition, the potential difference across AB will be equal to the potential difference across AD and the potential difference across BC will be equal to the potential difference across CD....

De Sauty Bridge Components

De Sauty Bridge requires the following components:...

Construction of De Sauty Bridge

Let the variable resistors be R3 and R4 respectively. The standard capacitance is C2 and the unknown capacitance is C1. R3, R4, C1, and C2 are placed on four sides of a quadrilateral ABCD. We can place C1 on side AB, R1 on side BC, R4 on side CD and C2 on side AD of the quadrilateral. The galvanometer should be placed along the diagonal BD of the quadrilateral and the AC supply should also be placed along the other diagonal AC. The balanced condition can be obtained by varying the values of R3 and R4. The balance condition is independent of frequency. If either or both of the capacitors are imperfect or not free from dielectric losses, then the balance condition can be never obtained....

De Sauty Bridge Formula

C1=Unknown capacitance...

Phasor Diagram

Phasor diagrams are a graphical method of representing the magnitude and directional relationship between two or more alternating quantities. It can be used to show the relationship between voltage and current within passive components or the whole circuit. Let us mark the voltage drop across the capacitor C1 be V1 and the drop across C2 be V2. The voltage drop across the resistor R3 be V3 and the drop across R4 be V4. At balance condition, the current flowing through B-D will be zero and the voltage drops V1 and V2 will be equal to the voltage drops V3 and V4 respectively. To draw a phasor diagram take V3 or V4 as the reference axis. V1 and V2 are shown at right angles to V3 and V4 because the phase difference angle is 90....

Modified De Sauty Bridge

Since the original version of the De Sauty Bridge cold not be used with capacitors that are not free from dielectric los, Grover modified the bridge to provide accurate results for imperfect capacitors. In modified De sauty’s bridge, the two imperfect capacitors C1 and C2 are connected in series with two resistors R1 and R2. To measure capacitance with dielectric losses another two resistors r1 and r2 are connected to the two capacitors that give the loss component of their respective capacitor....

Phasor Diagram

The phasor diagram of the modified De Sauty bridge is shown in the figure below,...

Advantages and Disadvantages of De Sauty Bridge

Given Below are some of the Advantages and Disadvantages of De Sauty Bridge...

Applications of De Sauty Bridge

Measuring the values of unknown capacitance. De Sauty Bridge finds the unknown capacitance in terms of the standard capacitance.It can be used to find dielectric loss in capacitorsThe De Sauty Bridge offers high precision and accuracy compared to other bridges. So it is used in applications where precise values are needed like laboratories. It can be used to measure the impedance, which includes both reactance and resistance. This will be helpful in analyzing circuits that contain elements like inductors and capacitors.De Sauty Bridge is widely used in engineering applications like Electric machines, Power systems etc....

Conclusion

De Sauty Bridge is an AC bridge used to find the unknown capacitance in an electrical circuit. It is an important instrument used in the field of electrical engineering to measure the capacitance and other components in an electrical circuit. The main advantage of the De Sauty Bridge is its simple circuit design and uncomplicated calculations. The De Sauty bridge offers high accuracy and precision compared to other bridge circuits. However, the main disadvantage is that it can only find the values of capacitors that are free from dielectric loss. To overcome this disadvantage a modified version of the De Sauty bridge is used....

Solved Examples

In a De Sauty Bridge arm BC contains a resistor of value 1400Ω, arm AD contains a capacitor of 0.15µF and arm CD contains a resistor of 1800Ω.If the bridge is in a balanced state, find the unknown capacitance in arm AB....

FAQs on De Sauty Bridge

What is De Sauty Bridge?...