HACETTEPE UNIVERSITY
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
ELE 271 MEASUREMENT LABORATORY
2002-2003 FALL
RULES
I.
There will be 7 experiments and 6 quizzes in the laboratory program. Each
quizzes will be performed at the beginning of experiment for each group.
II.
Everyone should attend the lab. on allocated hours.
III.
If one does not attend more than one experiment he/she will take the grade F1.
IV.
Please read the experimental sheets before the experiments and try to solve the
problems in the preliminary work section and submit the preliminary work on the
day you perform the experiment.
Grading will be as follows :
Preliminary work
Experimental Report
Quiz
Final examination
: 7%
: 7%
: 42%
: 44%
Mehmet Ersan KAYKUSUZ
Kurtuluş Erinç AKDOĞAN
Gökçen CİVAN
0
HACETTEPE UNIVERSITY
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
ELE 271 MEASUREMENT LABORATORY
EXPERIMENT #1
MEASUREMENT OF VOLTAGE, CURRENT AND RESISTANCE
Object :
Measurement of current, voltage and resistance quantities by use of an AVO
meter and the experimental verification of Kirchoff's current and voltage laws.
1. INTRODUCTION :
1.1 AVO meter :
AVO meter is an instrument for measuring the values of current, voltage and
resistance. In case of appropriate ranges and modes of operation are selected, it
is possible to reach a correct measurement. Otherwise either the meter could be
damaged or the measurement is incorrect.
The symbolic representation of the AVO meter is shown in Fig 1.
The output terminals are denoted by the signs (+) and (-).
Fig 1. Symbolic representation of the AVO meter
1.2. AVO meter in current mode ( Ammeter )
In order to use the AVO meter as an ammeter, one has to observe the following
directions :
* The switches on the meter should be selected appropriately.
* The ammeter should be connected in series to any network since its internal
resistance is supposed to be zero.
* In direct current (DC) circuits, the current flow direction is important. The
ammeter should be connected in such a way that the current enters the
instrument from the (+) terminal. Otherwise the pointer will deflect in the reverse
direction.
As an example, refer to Fig.2.
1
If one wants to measure the current I2 in the figure, first, all the switches must
be properly set, so that the meter acts as an ammeter. Then the meter terminals
are connected to the branch in series. Other currents in other branches could be
measured in a similar manner.
I1
R1
+ V1
R3
a
I3
c
I2
+ V3
+
+
+
V
R2
V2
-
-
R4
V4
-
b
Fig.2.
I1
R1
R3
a
c
+ I2
+
V
-
R4
R2
b
Fig 3. Current measurement
1.2. AVO meter in voltage mode (Voltmeter ) :
* As in the ammeter case, one has to set the switches on the meter properly, so
that the meter acts as a voltmeter.
* The voltmeters are always connected to the network in parallel, as its internal
resistance is supposed to be infinite.
* In alternating current (AC) circuits, the connection of the terminal polarities are
not important. But for DC measurements one has to pay attention for the
appropriate connections.
As an example, if voltage V2 is to be measured in Fig.4., the meter terminals
must be connected as shown below.
2
voltmeter
R1
R3
+ V3 -
a
d
+
V
R4
R2
c
b
Fig.4. Measurement of voltage V3
1.3. AVO meter in resistance mode (Ohmmeter)
The details are given in the course notes.
2. Resistance Color Coding :
The most widely used resistances are of carbon type. There exists three or four
color bands on the resistance body, indicating the ohmic values and tolerances.
In order to achieve a correct reading, one has to hold the resistance in such a
way that the bands are close to the left hand side, then the ohmic value is given
by the formula;
R= AB x 10 C
A
B
C
 D % ohms
D
Fig.5 Resistor
Resistor Color Codes
Color
Black
Brown
Red
Orange
Yellow
Green
Blue
Violet
Gray
White
Gold
Silver
Value
0
1
2
3
4
5
6
7
8
9
-1 (only for band C ) 5 ( for band D)
-2 (only for band C) 10 ( for band D)
Table 1. Resistor color codes
3
3. PRELIMINARY WORK :
3.1. Calculate the values of the currents I, I1,I2, I3 I4 and the voltages V1, V2,
V3,V4, V5 in Fig.6. Show the meter connections for these measurements.
I
I2
1
I4
I3
V2
I1
12 A
1
V4
V3 2
V1 2
V5
2
Fig 6.
3.2. For the circuit given in Fig.7, the values of R1 and V1 are given. Find out
the values of R2 and I2.
R1=3
I= ?
V1=6v
R2 = ?
6 v.
Fig. 7
3.3. Find the equivalent resistance Rab between points a and b for the circuit in
Fig.8.
1
5
a
1
Rab
1
12
2
6
2
b
5
1
1
Fig.8.
4
3.4. For the circuit shown in Fig.9., the value of R2 is required to be measured.
Why does not such a connection give the correct value? Redraw the circuit
showing the true connections.
R1
R2
V
ohmmeter
Fig 9.
3.5. Fig 10. shows a carbon resistor.
A
B
C
D
Fig. 10
For each of the resistance values given, write down the correct color bands.
a) 100  10%
b) 120  5%
c) 220  20%
d) 330  10%
3.6. For the resistor shown in Fig.10, color bands of A, B, C and D are given
below.
Write down the values of the resistors and their tolerances.
a)
b)
c)
d)
e)
A
Red
Red
Green
Violet
Red
B
Black
Red
Blue
Gray
White
C
Red
Brown
Gold
Orange
Orange
D
Silver
Gold
Gold
Silver
Gold
5
4. EXPERIMENTAL WORK :
Set-up the circuit shown in Fig 11.
I
I
I2
a
220
b
I4
V2
e
V4
I1
V1
100
I3
330
V3
220
120
V5
10 mA
c
d
Figure 11.
f
4.1 Measure the values of currents I, I1 I2, I3 ,I4 and voltages V1,V2,V3,V4,V5
by use of the AVO meter.
4.2 Disconnect the current source at points a and c. Measure the value of Rac.
4.3 Measure the values of each resistor with an ohmmeter after disconnecting it
from the circuit.
5. RESULTS and CONCLUSION :
5.1. Make theoretical calculations for section 4.1 and compare the results with
the measured ones.
5.2. Using the experimental results, try to prove Kirchoff's current law at points
a and b.
5.3. Using the experimental results, try to prove Kirchoff's voltage law for the
closed loops abdca, befdb and abefdca.
5.4. Calculate the theoretical value of Rac and compare it with the measured
one.
5.5. Comment on the differences between the theoretical and experimental
results.
EQUIPMENT AND COMPONENTS :
DC power supply
10 mA. current source
AVO meter
Resistors : 100 (#1), 120 (#1), 220 (#2), 330 (#1)
6
HACETTEPE UNIVERSITY
DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
ELE 271 MEASUREMENT LABORATORY
EXPERIMENT #1
Experiment Date:
Group No
:
Group Members :
RESULTS :
4.1
I=
I1=
I2=
I3=
I4=
V1=
V2=
V3=
V4=
V5=
4.2 Rac =
4.3
R1=
R2=
R3=
R4=
R5=
7