Circuits i Lab 1 Post Report

8/11/2019 Circuits i Lab 1 Post Report

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EEL-3115L.001F13

Laboratory Experiment 1: Demonstration of

Circuit Laws/Theorems

Gregory Keener

U-51971841

9/11/2013

This lab report was written and assembled solely by myself, Gregory Keener. In-lab measurements were

taken in conjunction with my lab partner, Erin Ritter. Use of any portion of this lab report by any other

students (with the exception of measurements for Erin Ritter) constitutes cheating. In addition to being

reported to appropriate USF faculty, violators will be publicly ridiculed, berated, and/or cursed out in

front of large groups of people by me. This document is provided on Scribd.com for the sole purposes of

demonstrating proper lab report formatting and experimental methods. Copyright 2013. All rights

reserved. If you are an instructor and are receiving this document, please slap your student for me.

They're cheating in your course.

____________________________________________________ ________________


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Signature Date

Table of contents

Introduction and Objectives..2

Pre-lab Calculations..2

Materials and Equipment..4

Experimental Procedure5

Experimental Data.....8

Data Analysis..11

Experimental Concerns, Issues, and Future Improvements12

Conclusion...13

Works Cited15

List of Tables and Figures

Figure 2.1: Circuit Diagram of Circuit A3

Figure 2.2: Circuit Diagram of Circuit B3

Table 2.1: Circuit A Theoretical Values.3

Table 2.2: Circuit B Theoretical Values.4

Figure 4.1: Live of Circuit A...6

Figure 4.2 Live of Circuit B6


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Table 5.1: Circuit A Experimental Values.8

Table 5.2: Circuit B Experimental Values.10

1. Introduction and Objectives

This purpose of this lab was to learn the proper use of laboratory equipment, including

digital multimeters, power supplies, breadboards, and basic circuit components. To accomplish

this, two circuits were to be created as shown in the lab manual (refer to section 3. Experimental

Procedures for detailed layout). These circuits were to be used to verify that KVL, KCL, and the

Thevenin Theorem hold in a laboratory environment. In addition to reinforcing fundamental

circuit laws and theorems, this experiment provided the opportunity to gain hands-on

experience with professional lab equipment. Also, this experiment demonstrated how to measure

experimental values for node voltages, branch currents, Thevenin voltages, Norton currents,

resistor voltages, and Thevenin resistances.

2. Pre-lab Preparations and Calculations

In preparation for this experiment, circuits A and B (see fig. 2.1 and 2.2, respectively)

were analyzed using KVL, KCL, Thevenin Theorem, and basic circuit laws such as Ohms law.

For circuit A, the node voltages, resistor voltages, and branch currents were calculated for the

entire circuit. For circuit B, the Thevenin voltage, Norton current, and Thevenin resistance were

calculated by hand using basic circuit laws and theorems.


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Figure 2.1: Circuit A diagram Figure 2.2: Circuit B diagram

The theoretical values for Circuit A and Circuit B were then recorded and are listed in Tables 2.1

and 2.2, respectively.

Circuit A Theoretical Values

Node Voltages

V1 12V

V2 4.062V

V3 Not calculated, mistakenly read node 3 as

ground

Branch Currents

I1 3.777mA

I2 2.898mA

I3

Not calculated, mistakenly read node 3 as

ground

Resistor Voltages


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V1.5k 5.666V

V3.3k 2.901V

V910k 3.437V

V1k -2.901V

Table 2.1

Circuit B Theoretical Values

Thevenin and Norton Equivalents

Vth 6.974V

IN 11.9355mA

Rth 582.08

Table 2.2

3. Materials and Equipment

The following materials and equipment were used to obtain experimental values:

1x Agilent U8030A Triple Output DC Power Supply

1x HP3441A Digital Multimeter

1x 910 , W resistor

1x 3.3 k, W resistor

1x 1.5 k, W resistor

1x 1 k, W resistor


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1x Heavy duty, banana plug-to-alligator clip wiring set

1x Heavy duty, probe test lead set.

1x Elenco Precision Model 9433 breadboard circuit design station

Note: Jumper wires in graphic diagrams are for illustrative purposes only and were not used for

the experimental circuit. As such, they are not included in this section

4. Experimental Procedure

Two identical circuits were prepared on a breadboard in accordance with the

specifications listed for circuit A and circuit B in figures 2.1 and 2.2, respectively. Although the

two circuits extremely similar, and could therefore be interchanged via a small change in wiring,

separate circuits were prepared in advance of the experiment in order to save time. A live

illustration of these circuits are shown below (see figures 4.1 and 4.2).


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Figure 4.1: Live model of circuit A

Figure 4.2: Live model of circuit B

In this experiment, circuit A was tested first. For the first part of this experiment, the

power supply was set to provide a constant 12VDC to the circuit, with a maximum current of

10mA (the lowest current setting possible on the power supply used). In order to obtain the node

voltages, the voltage was taken from each node, using node zero as the ground point for the

probes. The circuit was not broken or modified during this series of measurements, thereby

causing the probes to be in parallel to the selected node during measurement. Next, the voltages

were measured across each resistor. Once again, the circuit was measured as-is. Then, the

current was measured through each resistor. For this series of measurements, one side of the

resistor was removed from the circuit. The circuit was then reconnected using the test lead

probes to short the previously created open circuit.


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After this was completed, the power supply was set to 0V and the resistances were

measured across each resistor while still in the circuit. Next, the power supply was turned off and

resistances were taken across each node. Once again, all resistors were left connected to the

circuit. Finally, each resistor was removed from the circuit and individually measured for

resistance using the digital multimeter.

Circuit B was the next system to be tested. For this circuit, the power supply was set to

provide two separate voltages to the circuit. As such, 8VDC and 12VDC signals were connected

to the circuit at the points shown in figure 4.2. The node voltages and voltages across each

resistor were measured using the same methods used for circuit A. Next, the open circuit voltage

was measured across node 3 and 4. Then, a short circuit was created along nodes 3 and 4 using

the probe kit. The resulting value was recorded as the Norton current. Finally, the power supply

connections were removed and the circuit was shorted along these points. The resistance between

nodes 3 and 4 was then recorded as the Thevenin voltage, thereby concluding the experiment.

5. Experimental Data

Circuit A Experimental Values

Node Voltages

Measurement By-hand Experimental % Error

V1 12V 12.001V .00833%

V2

4.062V

6.335V

35.88%

V3 Not calculated,

mistakenly read node 3

as ground

3.442V N/A


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Branch Currents

Measurement

By-hand

Experimental

%Error

IR1 3.777mA 3.825mA 1.25%

IR2 2.898mA .896mA 223.44%

IR3 Not calculated,

mistakenly read node 3

as ground

2.942mA N/A

IR4

3.777mA

3.839mA

1.62%

Resistor Voltages


V1.5k 5.666V 5.664V .035%

V3.3k 2.901V 2.912V 0.38%

V910 3.437V 3.422V 0.44%

V1k -2.901V -2.912V 0.38%

Node Resistances


R(0-1)

N/A

3.122k

N/A

R(1-2) N/A 1.474k N/A

R(3-0) N/A 890.1 N/A

R(2-3) N/A 988.8 N/A


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Resistances of Resistors in Connected Circuit


R1.5k N/A 1.472k N/A

R3.3k N/A 3.247k N/A

R910k N/A 890.1 N/A

R1k N/A 988.8 N/A

Resistances of disconnected resistors


R1.5k N/A

1.740k

N/A

R3.3k N/A 757.77 N/A

R910k N/A 757.74 N/A

R1k N/A 890.44 N/A

Table 5.1

Circuit B Experimental Values

Node Voltages

Measurement

By-hand

Experimental

% Error

V1 N/A 7.99V N/A

V2 N/A 8.908V N/A

V3 N/A 3.090V N/A

V4 N/A -.3415V N/A

Resistor Voltages



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VR1 N/A 0.567V N/A

VR2 N/A 8.907V N/A

VR3 N/A 3.090V N/A

VR4 N/A -0.3415V N/A

Thevenin and Norton Equivalents


Vth -6.974V -3.089V 125.77%

IN

11.9355mA

5.337mA

123.64%

Rth 582.08 573.96 1.41%

Table 5.2

6. Data Analysis

For circuit A, the node voltage V2and branch current IR2showed extremely high percent errors

of 35.88% and 223.44%, respectively. After reviewing the experimental process and pre-lab

calculations, it was determined that the discrepancy was caused by incorrect analysis in the by-

hand calculations. Specifically, node 3 was mistakenly used as a reference node, in addition to

the reference node at node 0. This was due to misreading the circuit and overlooking R4(910

resistor) while performing circuit analysis. Once the circuit is correctly analyzed without node 3

being treated as an additional reference, the theoretical values of V2and IR2become 6.24V and

.835mA, respectively. This causes a percent error of 1.4996% for V2and 6.81%, respectively.

These values can also be determined using voltage and current division, in which they hold the

same respective values. All other calculations correlated properly with experimental results.


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The same error occurred during analysis of circuit B. In this case, node 4 was treated as a

reference node, in addition to the reference node at node 0. As a result, the Thevenin voltage

values had a percent error of 125.77%, while the Norton current showed a percent error of

123.64%. Once again, correct analysis of the circuit (by removing the ground from node 4)

substantially reduced the percent error for both Vthand IN. Proper analysis resulted in a sub-4%

percentage error for both values. The experimental Thevenin resistance was within an acceptable

error margin of calculated values.

7. Experimental Concerns, Issues, and Future Improvements

While the experiment was ultimately successful, there were a few issues. First, the

breadboard circuits were configured incorrectly at first. This caused delays in completing the

experiment due to requiring time to troubleshoot anomalous multimeter readings (0 voltage).

This could have been avoided by designing the physical circuits in a manner that more closely

resembled circuit diagrams 1.1 and 1.2. Instead, the circuits were configured in a manner that

used as little breadboard space as possible, causing them to appear cluttered and causing

confusion during assembly. An example of this cleaner layout is given in figures 4.1 and 4.2.

A substantial amount of time was also used for familiarization with both the digital

multimeter and power supply. Since neither party performing this experiment had any experience

with the specific equipment models being used, a large amount of laboratory time was wasted

attempting to figure out the proper use of said equipment. Specifically, setting maximum

currents on the power supply and ensuring the proper test lead connections on the digital

multimeter proved to be time-consuming due to lack of experience. This could have been easily

avoided by reading the instruction manuals provided in the lab manual prior to arriving in the

laboratory.


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theorem, current/voltage division, and resistance combinations to the experiment itself yields

values that are within 1-2% of expected values. As such, the experiment was able to successfully

verify the aforementioned circuit laws and theorems.

Additionally, this experiment provided invaluable experience with both the digital

multimeters and power supplies used in this course. This experience vastly increased the

experimenters proficiency and confidence in dealing with such equipment in a professional

laboratory environment. In the future, this learning curve should become irrelevant, as most basic

operations of said lab equipment have now been performed and mastered.

9. Works Cited

None

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