Circuits lab report # 1 / An Introduction to Laboratory Equipment and Ohm’s Law + PSpice
Christoph Hoening / Carla Limpias
Department of Physics and Engineering
Elizabethtown College, Elizabethtown, PA
Email: paradac@etown.edu / hoeningc@etown.edu
Introduction:
The main purpose of this lab was to accustom ourselves with the Lab equipment necessary for
future circuit labs. Therefore, we were given a circuit diagram, a breadboard, a digital multimeter and all necessary accessories to perform the given tasks.
Procedures:
Our first task was to check on the breadboard with the digital multi-meter to determine which
rows and columns are connected. First, we set the digital multi-meter to kilo Ohms since we
want to measure the resistance between the columns and rows. If a connection exists, the device
will display 00.0 kilo Ohms because there is a connection available with no resistance. In case of
no connection, the multi-meter displays OL, which means
Overload. Because of the non-existing connection between
the rows and columns, the device has a resistance value that is
too large and cannot be displayed. In order to measure
between rows and columns we stuck wire into the breadboard
and connected the multi-meters alligator wires to it. Our
findings are demonstrated in Figure1.
Apendix1 displays pictures of our procedure.
Figure1. Electrical contact on breadboard
Next, we measured the resistance of the four resistors given to us. We used the digital multimeter with the alligator wire clips and attached them to the wire ends of the resistors. The
measured values are demonstrated in Table1. Attached in Appendix 2 is how the multi-meter
was connected to the resistors. When the range of the multi-meter is too high for the Ohms, the
results can be confusing. One might assume that there is no resistance because significant
numbers are cut off due to a range that is too high. For instance, kilo Ω is too big for the 100 Ω
and 200 Ω resistors. We therefore chose the range 200Ω on
the multi-meter, that provides the best accuracy. The 560 and
1500 Ω resistors are too big for the 200Ω range and the
multi-meter displayed an Overload. Consequently, we
adjusted the range to 2-kilo Ω for the best readings.
Table1. Measured values in Ω
After the first exercise with the multi-meter and the breadboard, we were instructed to build the
circuit shown in Figure2 on our breadboard. We used different
lengths of wires and the given resistors to build the circuit on
our breadboard shown in Figure3. After we successfully built
the circuit, we measured the different currents and voltages
with the multi-meter, with an input voltage 𝑉 1 providing 15V. Table2 displays our results.
0
R1
R2
1.5k
200
1-5 V
R5
560
R3
100
Figure2.Given Circuit
V1
vR1
iR1
vR2
iR2
vR3
iR3
vR4
iR4
1
0.882V
0.601mA
0.077V
0.395mA
0.039V
0.393mA
0.116V
0.210mA
2
1.767V
1.213mA
0.155V
0.782mA
0.078V
0.782mA
0.232V
0.419mA
3
2.640V
1.807mA
0.232V
1.176mA
0.117V
1.177mA
0.348V
0.625mA
4
3.53V
2.4mA
0.309V
1.572mA
0.156V
1.565mA
0.465V
0.832mA
5
4.41V
3.01mA
0.387V
1.966mA
0.196V
1.962mA
0.584V
1.036mA
Table2. Measure Currents and Voltages
Figure3.
Built circuit
Possible errors could have occurred because the multi-meter was not properly adjusted to
provide the most accurate reading. Furthermore, it was crucial to make sure to measure the
current in sequence and the voltage in parallel just as shown in the sketch of Figure4.
We also used equation1 to check our measured
voltage. In addition, equation2 and equation3
helped to determine the measured current.
Example calculations are attached in Appendix 3.
Equation1. 𝑉𝑖𝑛
Equation2.
= 𝑉𝑅1 + 𝑉𝑅4
𝐼𝑅1 =
Equation3. 𝐼𝑅1
𝑉𝑅1
𝑅1
Figure4.
= 𝐼𝑅4 + 𝐼𝑅2
Furthermore, we simulated this circuit in PSPICE with the input Voltage V 1 as 1V and 5V. The
resulting voltages and currents for the simulation of input Voltage 1V are shown in the
schematics of Figure 5 and Figure 6.
Figure5
Voltage
..
Table 3 compares the measured results with
the simulated results and displays the
percentage error. The example calculations
and the circuit schematic for the 5V
Figure 6
Current.
simulation can be retrieved from
Appendix4. The calculated errors are very
small and reflect the accuracy of the
computer program. In nature, we will
lose some of that accuracy due to nonperfect wires with wire resistance and
loose connections. Energy can get lost in
the distance of the wire due to wire
resistance. However, due to the small
circuit this error is very small. Another
occurring error leading to less accurate
values could be human error in properly
adjusting the voltage source or using the
wrong scale on the multi-meter.
V1
1
5
Sim 1
Sim 5
4.42V
%
error
Sim 1
0.23
%
error
Sim 2
0.23
vR1
0.882V
4.41V
0.884V
vR2
0.077V
0.387V
0.077V
0.384V
0.00
0.78
vR3
0.039V
vR4
0.116V
0.196V
0.038V
0.192V
2.63
2.08
0.584V
0.115V
0.576V
0.87
1.39
iR1
iR2
0.601mA
.301mA
0.59mA
.295mA
1.86
2.03
0.395mA
.1966mA
.381mA
.192mA
3.67
2.39
iR3
0.393mA
.1962mA
.384mA
.192mA
2.34
2.19
iR4
0.210mA
.1036mA
.206mA
.103mA
1.94
.58
Table3.
The last task in this week’s labs was to
simulate two circuits in PSPICE which the
resulting schematics are shown in Figure7
and Figure8. The purpose of this task was
to familiarize ourselves with PSPICE and
know how to build and simulate circuits.
Figure6.
Figure7.
Conclusion:
This lab helped us learn how to use the multi-meter the breadboard and all the other lab
equipment in order to build a desired circuit to specifications. Furthermore, it demonstrated how
voltage and current needs to be measured differently on circuits. Failure to do so would result in
wrong measurements. In addition, it demonstrated how the given Equations 1-3 help validate the
measured values. The application of the software simulation PSPICE displayed that simulated
circuits put out perfect values for current and voltage. However, a circuit built on the breadboard
is much more complicated. Factors such as wire resistance, loose connections, air resistance play
a major role on the accuracy of the data. Moreover, the multi-meter might not perform perfect
readings or the scale of the readings is not adjusted properly. Even though we tried to pay
attention to all these possible error sources, we got minor errors below 5%, which was satisfying
for our needs.
References:
Lab1, Handout, Dr. Estrada
https://www.raspberrypi.org/forums/viewtopic.php?f=91&t=110357 => retrieved Figure1.
Appendix1:
Overload the shown sections are not
connected
Overload the shown sections are not
connected
No Overload the shown sections are
connected
Overload the shown sections are not
connected
No Overload the shown sections are
connected
No Overload the shown sections are
connected
Appendix2:
Overload the shown sections are not
connected
Measuring of the different resistors.
Appendix3:
Equation1. 𝑉𝑖𝑛 = 𝑉𝑅1 + 𝑉𝑅4
Equation2. 𝐼𝑅1 =
𝑉𝑅1
=> 𝑉𝑖𝑛 = 0.882𝑉 + 0.116𝑉
=> 𝐼𝑅1 =
𝑅1
Equation3. 𝐼𝑅1 = 𝐼𝑅4 + 𝐼𝑅2
0.882𝑉
1.5𝑘𝛺
=> 𝐼𝑅1 = 0.210𝑚𝐴 + 0.395𝑚𝐴
=>
𝑉𝑖𝑛 = 0.998𝑉
=>
𝐼𝑅1 = 0.588𝑚𝐴
=>
𝐼𝑅1 = 0.605𝑚𝐴
Appendix 4:
In order to get the correct voltages one must subtract the voltage differences at the resistors.
Example.
Resistor1 with 1V input:
1.000V-115.2mV=0.884V
To get the current one must divide voltage by the resistance
Example.
Resistor 1 with 1V input:
0.882V/.0015kµ = 588mA
The Error was calculated with this equation
(𝑉𝑎𝑙𝑢𝑒𝑚𝑒𝑎𝑠𝑢𝑟𝑒𝑑 −𝑉𝑎𝑙𝑢𝑒𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑 )
𝑉𝑎𝑙𝑢𝑒𝑠𝑖𝑚𝑢𝑙𝑎𝑡𝑒𝑑
×100
Circuit for 5V
Current for 5V