In this article, you will find the study notes on Bridges which will cover the topics such as Maxwell’s inductance bridge, Maxwell’s inductance-capacitance bridge, Hay’s bridge, Anderson’s bridge, Owne’s bridge, De-Sauty Bridge, Wein’s Bridge, D.C Potentiometer & A.C Potentiometer etc.
AC Bridges: AC bridges are used to measure self-inductance, mutual inductance, capacitance and frequency.
Types of Sources
- At low frequency, the power line is used as a source.
- At high frequency, the electronic oscillator is used as a source
Types of Detectors
- Vibration galvanometer at low power frequency and audio frequency (up to 1000 Hz)
- Headphones at an audio frequency (250 Hz to 4 kHz)
- Tunable amplifier for frequency range (10 Hz to 100 kHz)
General Bridge Circuit
At balanced bridge
Magnitude condition
Angle condition
For balanced bridge both the magnitude
Measurement of Self Inductance
- Maxwell’s inductance bridge
- Maxwell’s inductance-capacitance bridge
- Hay’s bridge
- Anderson’s bridge
- Owne’s bridge
Maxwell’s Inductance Bridge
Where, L1 = Unknown inductance of resistance R1
L2 = Variable induactance
R2 = Standard variable resistance
R3, R4 = Fixed non-inductance resistance
Maxwell’s Inductance - Capacitance Bridge
Q-factor,
Q-factor range 1 < Q < 10, for medium Q-coils
Where, R4 = Variable non-inductive resistance
C4 = Standard variable capacitance
Note: If C4 is fixed, then balanced bridge obtained as
- Either by varying R2 and R4.
- Put a resistance in series with L1 and varying R4.
Hay’s Bridge
Where, C4 = Standard capacitance
Q-factor
for Q > 10 i.e., high Q-coils
L1 = R2R3C4
Anderson’s Bridge
Where, L1 = Unknown self-inductance with an internal resistance R1
R2, R3, R4 = Fixed standard non-inductive resistance
r = A variable resistance
C = A fixed capacitance
- Anderson’s bridge is suitable for small Q-factor i.e., Q < 1.
- It can also be used for the measurement of capacitance in terms of inductance.
Key Points
- Maxwell’s bridge is used to measure the inductance of a low Q-inductor.
- Hay bridge is used to measure the inductance of a high Q-inductor.
- Inductance is measured in terms of capacitance, resistance by Anderson’s bridge.
Owen’s Bridge
Where, L1 = Unknown self-inductance with internal resistance R1
R2 = Variable non-inductive resistance
R3 = Fixed standard non-inductive resistance
C2 = Standard variable capacitor
C4 = Fixed standard capacitor
Measurement of Capacitance
The capacitance can be measured with the help of the following bridges
De-Sauty Bridge
Where C1 = Unknown capacitor
C2 = Standard capacitor
R3, R4 = Fixed non-inductive resistance
The de-Sauty bridge can be used for the measurement of either air-cored or gas-filled capacitance only (lossless capacitor).
Schering Bridge
Dissipation factor D1 = tan δ = ωC1r1 = ωC4 R4
Where C1 = Unknown capacitor with loss component r1
C2 = Fixed standard capacitor
R3 = Fixed standard non-inductive resistance
C4 = Variable capacitor
R4 = Variable non-inductive resistance
Key Points
- High voltage Schering bridge is used for the determination of capacitance of insulators, capacitor bushings and insulating oil and other insulating materials.
- Schering bridge is also used to measurement of relative permittivity of dielectric materials.
- The Schering bridge is one of the most widely used AC bridges.
- In order to measure the low value of capacitance Schering bridge is used.
Measurement of Frequency
Frequency by Wein’s bridge.
Wein’s Bridge
Frequency,
For R1 = R2 = R
and C1 = C2 = C
and C1 = C2 = C
- Wein’s bridge used as a notch Filter in harmonic distortion analyzer.
- A frequency isolator in high-frequency oscillator and amplifier circuit.
- A notch filter in a harmonics distortion analyzer where it is used to isolate and eliminate the fundamental frequency component from the output of the amplifier under test.
Comparison between Different Types of Bridges
You can avail of BYJU’S Exam Prep Online classroom program for all AE & JE Exams:
BYJU’S Exam Prep Online Classroom Program for AE & JE Exams (12+ Structured LIVE Courses)
You can avail of BYJU’S Exam Prep Test series specially designed for all AE & JE Exams:
BYJU’S Exam Prep Test Series AE & JE Get Unlimited Access to all (160+ Mock Tests)
Thanks
Team BYJU’S Exam Prep
Download BYJU’S Exam Prep APP, for the best Exam Preparation, Free Mock tests, Live Classes.
Comments
write a comment