PRACTICAL
4
AIM: - TEST THE CAPACITANCE BY
USING UNIVERSAL IMPEDANCE BRIDGE
v OBJECTIVE: - To find the capacitance of unknown
capacitor using Schering bridge. As a universal impedance bridge.
v APPARATUS :
Sl. NO.
|
NAME
|
TYPE
|
RANGE
|
QTY.
|
1
|
Schering bridge circuit
|
1 no
|
||
2.
|
Head phones
|
1 no.
|
||
3.
|
Decade capacitance
box
|
1 no.
|
||
4.
|
DMM
|
digital
|
1 no.
|
|
5.
|
Patch cards
|
1set
|
||
6
|
RPS
|
230v
|
1 no
|
|
7
|
Galvanometer
|
1 no
|
v CIRCUIT DIAGRAM:
For circuit diagram in PDF formate please click on the download link
v THEORY:
The Schering Bridge is
very widely used for the measurement of capacitance, dielectric loss and power
factor of capacitors. The advantage of using this bridge is that it can be
employed in both low voltage and high voltage measurements.
v FROM THE CIRCUIT
:
C1 is the unknown capacitance and
R1 is a resistance representing its loss
component
C2 is a standard air capacitor and it is loss
free
R3 & R4 are non-inductive
standard resistors.
R3 is fixed and R4 is variable
C4 is variable capacitors.
The detector may be a head phone or vibration
galvanometer
E is a low voltage a.c. source r 230v,50hz,supply
The bridge is balanced by adjusting
C4
and R4
For detail theory in PDF formate please click on the download link
v PROCEDURE :
1. Connections are made as per the circuit
diagram.
2. Connect the unknown capacitance ‘Cx’
between the terminals A & D.
3. Switch on the supply and vary the
Resistance knob (R1) until minimum sound is obtained from the loud
speaker.
4. Switch off the supply and measure the
Resistance (R1) between C & B by using DMM.
5. Repeat the above steps for different
values of capacitance & tabulate the readings.
6. Switch off the supply.
v PRECAUTIONS :
1. Avoid loose connections.
2. Resistance should be varied very smoothly.
3. Switch off the supply when the
resistance R1 is measured.
v FORMULA USED:
r1R4=
& C1=
Cx =(R4/R3) x C2
& C1=
Cx =(R4/R3) x C2
NOTE: the value of unknown capacitors is
C = 0.01μF
0.02 μF
0.03 μF
0.04 Μf
v OBSERVATION TABLE:-
sr.no
|
Cs (known
capacitance)
|
R4
|
R3
|
Cx=CsR4/R3
|
v CONCLUSION:-
FOR CIRCUIT DIAGRAM ...
PLEASE CLICK ON THE BELOW LINK...
