Bridges, Types of Bridges, Applications

2.  AC bridge
 DC bridge

3. Self- Inductance
 Maxwell’s Bridge
◦ Maxwell inductance bridge
◦ Maxwell inductance capacitance
bridge
 Hay’s Bridge
 Anderson bridge
 Owen’s Bridge
Capacitance
 De Saulty Bridge
 Schering’s bridge
Mutual Inductance
 Carey foster;
Heydweiller bridge
Frequency
 Wien’s Bridge

4. Four arm bridge – AC bridge
Inductance and capacitance can be measured
Galvanometer is replaced by Vibration Galvanometer

5. Maxwell inductance bridge
Used to measure inductance
◦ By comparison either with a standard variable self inductance.
Maxwell inductance capacitance bridge
Used to measure inductance
◦ By comparison either with a standard variable capacitance.

6. Advantages
1) The balance equation is independent of frequency.
2) The two balance equations are independent ; if we choose R4 and
C4 as variable elements.
3) The bridge yields simple expression for unknown L1 and R1 in
terms of known elements.
4) It is useful for measurement of wide range of inductance at power
and audio frequencies.

7. Disadvantages
 Variable standard capacitor will be expensive
 It cannot be used for measurement of high Q values, it is limited to
measure low Q value (1<Q<10)

8.  Modification of Maxwell bridge
 The difference in Maxwell’s bridge and Hay’s bridge is that the
◦ Hay’s bridge consists of resistance R4 in series with the standard
capacitor C4 in one of the ratio arms.
◦ Hays bridge requires only low values of R4 , while Maxwell
requires large value

9. Advantages
1) It is best suitable for the measurement of inductance with high Q,
typically greater than 10.
2) It gives very simple expression for Q factor in terms of elements in
the bridge.
Disadvantages
1) It is not suitable for the measurement of inductance with low Q,
typically lower than 10.

10.  Modification of Maxwell inductance capacitance bridge.
 Inductance is measured in terms of standard capacitor.
 Precise measurement of inductance over a wide range of values.

11. Advantages
1) In case of Anderson‘s bridge balance is easily obtained for low Q
coils than Maxwell bridge.
2) Fixed capacitor can be used
3) The bridge can be used for accurate determination of capacitance
in terms of inductance.
Disadvantages:
1) The Anderson’s bridge is complex than Maxwell bridge.
2) The additional junction point increases the difficulty of shielding
of the bridge.

12. Measurement of Inductance over a capacitance
Advantages
1) Balance equations are simple and does not contain any frequency
component
2) Can be used over a wide range of frequencies
Disadvantages
1) Variable capacitor is expensive
2) C2 tends to become large when measuring high Q values

13. Measurement of over a capacitance
 Does not give accurate results for dissipation factor
◦ Since value depends on the difference of quantities R1R4/R3 and R2.