İzmir University of Economics
EEE202 Electrical Circuits II
Title of the Experiment
Experiment – V
Measurement of Capacitance by Wien Bridge Circuits
Name-Surname of the Student
Student Number
E-Mail
Grade for the Lab (To be filled in by the instructor.)
Task
Pre-Lab Task 1
Pre-Lab Task 2
Pre-Lab Task 3
In-Lab Task 1
Total
Score
Background
Wien bridge and Maxwell-Wien bridge circuits are extensions of Wheatstone bridge circuits, which
are used to measure an unknown resistance. However, Wien bridge and Maxwell-Wien bridge
circuits are used to measure capacitance and inductance, respectively. The working principle is to
reach zero voltage across the bridge, i.e. A-B terminals, by adjusting the values of the other
elements such as capacitance-resistance boxes whose values are known. The bridge voltage VA-B
depends on the impedances Z1(jw), Z2(jw), Z3(jw) and ZX(jw). VA-B becomes zero when the
following equilibrium condition imposed on the impedance values are met:
Z1(jw) . Z3(jw) = Z2(jw) . ZX(jw).
Unknown impedance value can be calculated from this equation when the equilibrium is obtained
for a specific frequency and resistance-capacitance values chosen for Z1(jw), Z2(jw) and Z3(jw).
Z3
ZX
VS(t) = Vmcos(wt)
A
Z1
B
Z2
Pre-Lab Task 1
By determining Thevenin’s equivalent voltage across A-B terminals, derive the impedance condition
below for equilibrium:
Z1(jw) . Z3(jw) = Z2(jw) . ZX(jw).
Implementation of Pre-Lab Task 1
Pre-Lab Task 2
Obtain the equilibrium condition for the Wien bridge circuit given in Lab-Task 1 and then find a
relation for determining the unknown capacitance in terms of the known capacitance and resistance
values.
Implementation of Pre-Lab Task 2
Pre-Lab Task 3
Obtain the equilibrium condition for the Maxwell-Wien bridge circuit given in Lab-Task 2 and then
find a relation for determining the unknown inductance in terms of the known capacitance and
resistance values.
Implementation of Pre-Lab Task 3
In-Lab Task 1
Build up the following Wien Bridge circuit. By assigning the resistance values given in the table,
achieve the optimum CBox and CX values until reaching zero voltage VA-B across the A-B terminals.
Choose Vm = 5 V and f = 1 K Hz.
CX
VS(t) = Vmcos(2πft)
CBox
A
B
R1
R2
Implementation of In-Lab Task 1
R1
R2
10 k Ω
20 k Ω
5kΩ
20 k Ω
5kΩ
10 k Ω
2kΩ
10 k Ω
2kΩ
5kΩ
1kΩ
5kΩ
1kΩ
2kΩ
CX
CBox
VA-B
Student’s Evaluation of Learning Outcomes (Write in the following box what you have gained
from doing the Experiment V.)

The knowledge of ...

The skill of measuring/computing/calculating/determining/finding/simulating of...

The awareness/consciousness of...