LABORATORY MANUAL ECE 2110 - Electrical Engineering Lab I A companion course with ECE 2020 - Electric Circuits I Clemson University Holcombe Department of Electrical and Computer Engineering Clemson, SC 29634 Revised July 2010 Dr. J. E. Harriss
Revision Notes 2005 Author: O. C. Parks. Revised from earlier editions. 2010 Revised April-May 2010 by Dr. James E. Harriss. Minor corrections (typos, table labels, etc.). Revise Lab 2 for better introduction to the NI-ELVIS II. Reduce voltage in Lab 2, step 4 to avoid equipment damage. Revise Lab 10 for better clarity and to reduce measurement errors. Changed terms throughout (especially Lab 8) to conform to NI- ELVIS II. Change from PSpice to LT Spice. Minor revision in Appendix C. Add Revision Notes. 2010 Revised July 2010 by Dr. James E. Harriss. Eliminate Lab 12 (Lab Review and Presentations) to reduce the number of lab meetings to better fit the semester schedule. Change Lab 4 (LT Spice) Procedure 4 to illustrate the effect of component tolerance on circuit measurements. Move former Lab 5 (Statistical Analysis) to a later point in the course. Clemson University ECE Page ii July 2010 Edition
Contents Part I Course Information... iv Introduction... v Student Responsibilities... v Laboratory Teaching Assistant Responsibilities... v Faculty Coordinator Responsibilities... v Lab Policy and Grading:... vi Course Goals and Objectives... vi Use of Laboratory Instruments... viii Laboratory Notebooks and Reports... x The Laboratory Notebook:... x The Lab Report... x Format of Lab Report... xi Part II Laboratory Meetings... 0 Laboratory 1 Orientation... 1 Laboratory 2 Workstation Characteristics... 2 Laboratory 3 DC Measurements... 8 Laboratory 4 Introduction to LT Spice... 11 Laboratory 5 Network Theorems I... 15 Laboratory 6 Network Theorems II... 19 Laboratory 7 The Oscilloscope... 21 Laboratory 8 RC and RL Circuits... 24 Laboratory 9 Series RLC Circuits... 27 Laboratory 10 Statistical Analysis... 31 Laboratory 11 Design Lab... 33 Laboratory 12 Final Exam... 35 Part III Appendices... 36 Appendix A: Safety... 37 Appendix B: Fundamentals of Electrical Measurements... 41 Appendix C: Fundamentals of Statistical Analysis... 50 Appendix D: Resistor Identification... 58 Clemson University ECE Page iii July 2010 Edition
Part I Course Information Clemson University ECE Page iv July 2010 Edition
Introduction Introduction This course is intended to enhance the learning experience of the student in topics encountered in ECE 2020. In this lab, students are expected to get hands-on experience in using the basic measuring devices used in electrical engineering and in interpreting the results of measurement operations in terms of the concepts introduced in the first electrical circuits course. How the student performs in the lab depends on his/her preparation, participation, and teamwork. Each team member must participate in all aspects of the lab to insure a thorough understanding of the equipment and concepts. The student, lab teaching assistant, and faculty coordinator all have certain responsibilities toward successful completion of the lab's goals and objectives. Student Responsibilities: The student is expected to be prepared for each lab. Lab preparation includes reading the lab experiment and related textbook material. If you have questions or problems with the preparation, contact your Laboratory Teaching Assistant (LTA), but in a timely manner. Don't wait until an hour or two before and then expect to find the LTA immediately available. Active participation by each student in lab activities is expected. The student is expected to ask the teaching assistant any questions he/she may have. DO NOT MAKE COSTLY MISTAKES BECAUSE YOU DID NOT ASK A SIMPLE QUESTION. A large portion of the student's grade is determined in the comprehensive final exam, so understanding the concepts and procedure of each lab is necessary for successful completion of the lab. The student should remain alert and use common sense while performing a lab experiment. He/she is also responsible for keeping a professional and accurate record of the lab experiments in a laboratory notebook. Students should report any errors in the lab manual to the teaching assistant. Laboratory Teaching Assistant Responsibilities: The Laboratory Teaching Assistant (LTA) shall be completely familiar with each lab prior to class. The LTA shall provide the students with a syllabus and safety review during the first class. The syllabus shall include the LTA's office hours, telephone number, and the name of the faculty coordinator. The LTA is responsible for insuring that all the necessary equipment and/or preparations for the lab are available and in working condition. LAB EXPERIMENTS SHOULD BE CHECKED IN ADVANCE TO MAKE SURE EVERYTHING IS IN WORKING ORDER. The LTA should fully answer any questions posed by the students and supervise the students performing the lab experiments. The LTA is expected to grade the lab notebooks and reports in a fair and timely manner. The reports should be returned to the students in the next lab period following submission. The LTA should report any errors in the lab manual to the faculty coordinator. Faculty Coordinator Responsibilities: The faculty coordinator should insure that the laboratory is properly equipped, i.e., that the teaching assistants receive any equipment necessary to perform the experiments. The coordinator is responsible for supervising the teaching assistants and resolving any questions or problems that are identified by the teaching assistants or the students. The coordinator may supervise the Clemson University ECE Page v July 2010 Edition
Introduction format of the final exam for the lab. He/she is also responsible for making any necessary corrections to this manual. The faculty coordinator is responsible for insuring that the software version of the manual is continually updated and available. Lab Policy and Grading: The student should understand the following policy: ATTENDANCE: Attendance is mandatory and any absence must be for a valid excuse and must be documented. If the instructor is more than 15 minutes late, students may leave the lab. LAB RECORDS: The student must: 1) Keep all work in preparation of and obtained during lab in an approved NOTEBOOK; and 2) Prepare a lab report on selected experiments. GRADING POLICY: The final grade of this course is determined using the following criterion: Laboratory notebook and in-class work: 40% Lab reports: 40% Final exam: 20% In-class work will be determined by the teaching assistant, who, at his/her discretion may use team evaluations to aid in this decision. The final exam should contain a written part and a practical (physical operations) part. PRE-REQUISITES AND CO-REQUISITES: The lab course is to be taken during the same semester as ECE 2020, but receives a separate grade. If ECE 2020 is dropped, then ECE 2110 must be dropped also. Students are required to have completed both MTHSC 108 and PHYS 122 with a C or better grade in each. Students are also assumed to have completed a programming class and be familiar with the use of a computer-based word processor. THE INSTRUCTOR RESERVES THE RIGHT TO ALTER ANY PART OF THIS INFORMATION AT HIS/HER DISCRETION IF CIRCUMSTANCES SHOULD DICTATE. Any changes should be announced in class and distributed in writing to the students prior to their effect. Course Goals and Objectives: The Electrical Circuits Laboratory I is designed to provide the student with the knowledge to use basic measuring instruments and techniques with proficiency. These techniques are designed to complement the concepts introduced in ECE 2020. In addition, the student should learn how to record experimental results effectively and present these results in a written report. More explicitly, the class objectives are: Clemson University ECE Page vi July 2010 Edition
Introduction 1) To gain proficiency in the use of common measuring instruments. 2) To enhance understanding of basic electric circuit analysis concepts including: a) Independent and dependent sources. b) Passive circuit components (resistors, capacitors, inductors, and switches). c) Ohm's law, Kirchhoff's voltage law, and Kirchhoff's current law. d) Power and energy relations. e) Thévenin's theorem and Norton's theorem. f) Superposition. 3) To develop communication skills through: a) Maintenance of succinct but complete laboratory notebooks as permanent, written descriptions of procedures, results, and analyses. b) Verbal interchanges with the laboratory instructor and other students. c) Preparation of succinct but complete laboratory reports. 4) To compare theoretical predictions with experimental results and to resolve any apparent differences. Clemson University ECE Page vii July 2010 Edition
Use of Laboratory Instruments Use of Laboratory Instruments One of the major goals of this lab is to familiarize the student with the proper equipment and techniques for making electrical measurements. Some understanding of the lab instruments is necessary to avoid personal or equipment damage. By understanding the device's purpose and following a few simple rules, costly mistakes can be avoided. Ammeters and Voltmeters: The most common measurements are those of voltages and currents. Throughout this manual, the ammeter and voltmeter are represented as shown in Figure 1. Figure 1 - Ammeter and voltmeter. Ammeters are used to measure the flow of electrical current in a circuit. Theoretically, measuring devices should not affect the circuit being studied. Thus, for ammeters, it is important that their internal resistance be very small (ideally near zero) so they will not constrict the flow of current. However, if the ammeter is connected across a voltage difference, it will conduct a large current and damage the ammeter. Therefore, ammeters must always be connected in series in a circuit, never in parallel with a voltage source. High currents may also damage the needle on an analog ammeter. The high currents cause the needle to move too quickly, hitting the pin at the end of the scale. Always set the ammeter to the highest scale possible, then adjust downward to the appropriate level. Voltmeters are used to measure the potential difference between two points. Since the voltmeter should not affect the circuit, the voltmeters have very high (ideally infinite) impedance. Thus, the voltmeter should not draw any current, and not affect the circuit. In general, all devices have physical limits. These limits are specified by the device manufacturer and are referred to as the device rating. The ratings are usually expressed in terms of voltage limits, current limits, or power limits. It is up to the engineer to make sure that in device operation, these ratings (limit values) are not exceeded. The following rules provide a guideline for instrument protection. Clemson University ECE Page viii July 2010 Edition
Use of Laboratory Instruments Instrument Protection Rules: 1) Set instrument scales to the highest range before applying power. 2) Be sure instrument grounds are connected properly. Avoid accidental grounding of "hot" leads, i.e., those that are above ground potential. 3) Check polarity markings and connections of instruments carefully before connecting power. 4) Never connect an ammeter across a voltage source. Only connect ammeters in series with loads. 5) Do not exceed the voltage and current ratings of instruments or other circuit elements. This particularly applies to wattmeters since the current or voltage rating may be exceeded with the needle still on the scale. 6) Be sure the fuse and circuit breakers are of suitable value. When connecting electrical elements to make up a network in the laboratory, it is easy to lose track of various points in the network and accidently connect a wire to the wrong place. A procedure to follow that helps to avoid this is to connect the main series part of the network first, then go back and add the elements in parallel. As an element is added, place a small check by it on your circuit diagram. Then go back and verify all connections before turning on the power. One day someone's life may depend upon your making sure that all has been done correctly. Clemson University ECE Page ix July 2010 Edition
Laboratory Notebooks and Reports Laboratory Notebooks and Reports The Laboratory Notebook: The student records and interprets his/her experiments via the laboratory notebook and the laboratory report. The laboratory notebook is essential in recording the methodology and results of an experiment. In engineering practice, the laboratory notebook serves as an invaluable reference to the technique used in the lab and is essential when trying to duplicate a result or write a report. Therefore, it is important to learn to keep an accurate notebook. The laboratory notebook should 1) Be kept in a sewn and bound or spiral bound notebook. 2) Contain the experiment's title, the date, the equipment and instruments used, any pertinent circuit diagrams, the procedure used, the data (often in tables when several measurements have been made), and the analysis of the results. 3) Contain plots of data and sketches when these are appropriate in the recording and analysis of observations. 4) Be, an accurate and permanent record of the data obtained during the experiment and the analysis of the results. You will need this record when you are ready to prepare a lab report. The Lab Report: The laboratory report is the primary means of communicating your experience and conclusions to other professionals. In this course you will use the lab report to inform your LTA what you did and what you have learned from the experience. Engineering results are meaningless unless they can be communicated to others. Your laboratory report should be clear and concise. The lab report shall be typed on a word processor. As a guide, use the format on the next page. Use tables, diagrams, sketches, and plots, as necessary to show what you did, what was observed, and what conclusions you draw from this. Even though you will work with one or more lab partners, your report will be the result of your individual effort in order to provide you with practice in technical communication. You will be directed by your LTA to prepare a lab report on a few selected lab experiments during the semester. Your assignment might be different from your lab partner's assignment. Clemson University ECE Page x July 2010 Edition
Laboratory Notebooks and Reports Format of Lab Report: LABORATORY XX TITLE (Indicate the lab title and number) NAME - Give your name. LAB PARTNER(S) - Specify your lab partner's name. DATE - Indicate the date the lab was performed. OBJECTIVE - Clearly state the objective of performing the lab. EQUIPMENT USED - Indicate which equipment was used in performing the experiment. The manufacturer and model number should be specified. PROCEDURE - Provide a concise summary of the procedure used in the lab. Include any modifications to the experiment. DATA - Provide a record of the data obtained during the experiment. Data should be retrieved from the lab notebook and presented in a clear manner using tables. OBSERVATIONS AND DISCUSSIONS - The student should state what conclusions can be drawn from the experiment. Plots, charts, other graphical medium, and equations should be employed to illustrate the student's viewpoint. Sources of error and percent error should be noted here. QUESTIONS - Questions pertaining to the lab may be answered here. These questions may be answered after the lab is over. CONCLUSIONS - The student should present conclusions which may be logically deduced from his/her data and observations. SIGNATURE - Sign your report at the end. Include the statement - "This report is accurate to the best of my knowledge and is a true representation of my laboratory results." Clemson University ECE Page xi July 2010 Edition
Part II Laboratory Meetings Clemson University ECE July 2010 Edition
Laboratory 1: Orientation Laboratory 1 Orientation Introduction: In the first lab period, the students should become familiar with the location of equipment and components in the lab, the course requirements, and the teaching instructor. Students should also make sure that they have all of the co-requisites and pre-requisites for the course at this time. Objective: To familiarize the students with the lab facilities, equipment, standard operating procedures, lab safety, and the course requirements. Preparation: Read the introduction and Appendix A, Safety, in this manual. Equipment Needed: ECE 2110 lab manual. Procedure: 1) During the first laboratory period, the instructor will provide the students with a general idea of what is expected from them in this course. Each student will receive a copy of the syllabus, stating the instructor's office hours and telephone number. In addition, the instructor will review the safety concepts of the course. 2) The instructor will indicate which word processor should be used for the lab reports. The students should familiarize themselves with the preferred word processor software. 3) During this period, the instructor will briefly review the equipment which will be used throughout the semester. The location of instruments, equipment, and components (e.g. resistors, capacitors, connecting wiring) will be indicated. The guidelines for instrument use will be reviewed. Probing Further: 1) During the next period, the instructor may ask questions or give a quiz to determine if you have read the introductory material. As a professional engineer, it will be your responsibility to prepare yourself to do your job correctly. Learn as much as you can "up front. You will find that as a practicing professional if you wait until the last minute, you might have to pay a very painful price emotionally, financially, and professionally. Report: No report is due next time. Clemson University ECE Page 1 July 2010 Edition
Laboratory 2: Workstation Characteristics Laboratory 2 Workstation Characteristics Introduction: Every engineer relies on equipment to drive and measure an electrical system under study. These devices are rarely ideal, and have their own internal characteristics which must be considered. The internal characteristics of various devices often have a significant effect on circuit operation. This may be accounted for in circuit design and analysis to more adequately predict actual operation in the lab. Students and engineers should understand the internal characteristics of the equipment they are using. This experiment will explore some of those characteristics for the NI- ELVIS workstations used in this course. Objective: By the end of this lab, the student should know how to determine the internal resistance of meters and sources. The student should understand how the internal resistance of these instruments affects the measurements. Preparation: Reading: Read the section Use of Lab instruments and Appendix B, Fundamentals of Electrical Measurement, in this manual. Writing: In your laboratory notebook sketch the circuit diagram for each part of the procedure and create tables formatted to enter your data. Equipment Needed: NI-ELVIS workstation. Resistance substitution box. Resistors: 1.0 kω Procedure: Getting Started: a. Turn on computer. b. Turn on NI-ELVIS power switch (right corner on the back). c. Turn on the NI-ELVIS Prototyping Board Power switch (at upper right corner, on top). d. Launch NI-ELVISMX INSTRUMENTS program. e. Launch the NI-ELVIS DMM instrument. f. Launch the NI-ELVIS VPS (Variable Power Supply) instrument. g. Arrange the instruments on the computer screen for your convenience. h. Set DMM to measure DC Volts. Specify the range to be 60V. Note: The various range scales of voltmeters, ammeters, and similar measurement instruments are achieved by changing the internal resistances of the instruments. Therefore, when measuring the internal resistance of an instrument, it is important to set the Clemson University ECE Page 2 July 2010 Edition
Laboratory 2: Workstation Characteristics instrument s range to one value and not change it until the measurements are completed. Therefore, choose a scale that will allow making the desired measurements. 1) NULL OFFSET for the voltmeter: Electrical drift sometimes causes shifts in the ZERO point indicated by measurement instruments. Often the shift is inconsequential, but sometimes it is significant compared to the actual signal being measured. To eliminate the shift, the NI-ELVIS provides a NULL OFFSET function that subtracts the value indicated at the instant NULL OFFSET is turned on. This is just like subtracting the tare weight of a container on a laboratory balance before weighing a material. To set the voltmeter s NULL OFFSET: Plug leads into the DMM VΩ and COM jacks, clip the leads together, let the voltage reading stabilize, and turn on Null Offset. 2) Measure DC resistance of the DMM Voltmeter: Voltmeters have an internal electrical resistance. Ideally a voltmeter would have infinite resistance, so no current would flow through it and so the meter would not affect voltages throughout the circuit. But real meters are not ideal. In this exercise you will measure the DC resistance of the DMM voltmeter. a. Set the VPS Supply + voltage to +10.00 Volts. STOP the VPS. b. Set up the circuit as shown in Figure 2.1, using the NI-ELVIS DMM for the voltmeter and the VPS for the power supply. R 10V + V Voltmeter with internal resistance R Vi Figure 2.1 - Circuit diagram to measure the internal resistance of the voltmeter. c. Set the resistor R to 0Ω by shorting the resistor s leads. RUN the VPS and record the voltage indicated by the meter. Remove the short across R. d. Increase the resistance R so that the meter reading drops by a significant fraction (up to about one half) of the original value. (Hint: R will need to be in the range of MΩ.) Record the final resistance R and measured voltage. e. STOP the VPS. f. Use the DMM ohmmeter to measure the actual resistance R, rather than relying on the indicated settings of the substitution box. Record the measured value. (Anytime you Clemson University ECE Page 3 July 2010 Edition
Laboratory 2: Workstation Characteristics make such measurements, it may be instructive to record results at a few intermediate values of R as well, for corroborative calculations.) g. From these readings, use voltage division to calculate RVi, the equivalent internal resistance of the voltmeter. 3) Measure DC resistance of the DMM Ammeter: Ammeters also have an internal electrical resistance. Ideally an ammeter would have no resistance (0 Ω) so that it would not alter the current flow it is trying to measure. In this exercise you will measure the DC resistance of the real DMM ammeter. a. Set the VPS Supply + voltage to +10.00 Volts. RUN the VPS and measure the actual voltage using the DMM voltmeter. Record the actual voltage. STOP the VPS. b. To use the DMM as an ammeter, move the DMM cables to A and COM and switch the DMM to measure DC Amps. c. Set up the circuit as shown in Figure 2.2, using the NI-ELVIS DMM for the ammeter and the VPS for the power supply. 1kΩ 10V + Ammeter with internal resistance R Ai A R Figure 2.2 - Circuit diagram to measure the internal resistance of the ammeter. d. With the VPS STOPPED, null the ammeter display value to obtain a reasonable zero reading. d. NULL the ammeter: Disconnect one lead of the ammeter (so no current will flow) and null the ammeter display value to obtain a reasonable zero reading. Reconnect the ammeter lead to the circuit. e. Set the resistor R to 1 MΩ resistance. RUN the VPS. In a table, record the resistance R and the current indicated by the ammeter. f. Adjust R to 100kΩ. In your table, record the resistance R and the current indicated by the ammeter. g. Continue to decrease the resistance R until the ammeter reading drops by a significant fraction (up to about one half) of the original value. Record the final resistance R and measured current. Clemson University ECE Page 4 July 2010 Edition
Laboratory 2: Workstation Characteristics h. Use the DMM ohmmeter to measure the actual final resistance R, rather than relying on the indicated settings of the substitution box. (You will need to connect the DMM cables to VΩ and COM for this measurement.) i. From these readings, use current division to calculate RAi, the equivalent internal resistance of the ammeter. 4) Measure Output Resistance of VPS Supply +: Power sources also have internal resistance, which cause the units to get hot and which limit the amount of current the sources can deliver. The internal resistance may also be chosen to match a power source to the system it is powering. In this step you will measure the internal resistance of the NI-ELVIS s variable power supply, VPS. a. STOP the VPS. b. Set the VPS Supply + voltage to +0.5 Volts. c. Use the DMM to measure the actual voltage. To do this, switch the DMM to DC V mode and choose AUTO Mode. Move the DMM leads to VΩ and COM and connect the DMM leads to SUPPLY + output and GROUND. RUN the VPS and measure the actual voltage with the DMM voltmeter. Record the actual voltage. STOP the VPS. Note: If you null the voltmeter, be sure you do so by disconnecting the DMM leads from the circuit and shorting the leads together. Even with the VPS STOPPED, a small but significant voltage may exist. d. Construct the circuit shown in Figure 2.3. R VPS R VPS 0.5V + A Figure 2.3 - Circuit diagram for measuring the internal resistance of the workstation power supply. e. Adjust the resistor R to 10kΩ. RUN the VPS. Record the resistance R and the measured voltage in a table. f. Adjust the resistance R so that the meter reading drops by a significant fraction (up to about one half) of the original value. Record the R and V values in the table. CAUTION: The resistors in the substitution box are rated to handle at most 0.3 Watt power (Power = V²/R). If you exceed that limit, you will likely damage both the resistors and the power supply. Clemson University ECE Page 5 July 2010 Edition
Laboratory 2: Workstation Characteristics g. From these readings, use voltage division to determine RVPS, the equivalent internal resistance of the voltage source VPS. 5) Measure Output Resistance of the Function Generator: Repeat Part 4 using the Function Generator FGEN instead of VPS for the power source. a. Construct the circuit shown in Figure 2.4. Function Generator R FGEN V R V p-p = 1.414 V Figure 2.4 Circuit diagram to measure internal resistance of the Function Generator FGEN. b. Set the FGEN to output a sine wave with p-p amplitude of 1.41V and frequency 100 Hz. c. Set the DMM to measure AC Volts. Keep in mind that the voltmeter s display shows the value of RMS voltage, where for a sinusoidal waveform, V RMS = V peak = V p p. 2 2 2 d. Adjust the resistor R to 100 kω. RUN the FGEN. Record the resistance and the measured voltage in a table. e. Adjust the resistance R so that the meter reading drops by a significant fraction (up to about one half) of the original value. Record the R and V values in the table. f. From these readings, use voltage division to determine RFGEN, the equivalent internal resistance of the Function Generator. Probing Further: 1) Based on your estimates of the internal resistance of the voltmeters and ammeters used in these experiments, what would be the values of internal resistance of these meters if, in each case, the range used had been a factor of 10 larger than the range you actually used? Refer to Appendix B for the equivalent circuit models of the meters to guide your thinking about the answer to this question. 2) Given your values for the internal resistances of the DC source and the function generator, what do you think is the maximum amount of current that can be supplied by each source? Clemson University ECE Page 6 July 2010 Edition
Laboratory 2: Workstation Characteristics 3) How does the voltmeter s resistance affect measurements? Consider the circuit shown in Figure 2.5, and assume that the power supply is ideal. 100kΩ 10V + V R Figure 2.5 - Circuit diagram for measurements to determine the effect of voltmeter internal resistance on measurement accuracy. For resistance values R = 1kΩ, 100kΩ, and 10MΩ, calculate the voltage that would be displayed on an ideal voltmeter (i.e., if it had infinite resistance). Repeat the calculation using the real internal resistance you measured in step 2. Show your work in your lab book and display your results in a table such as shown here: R(Ω) V ideal V real 1 k 100 k 10 M Briefly discuss the significance of these results. Report: Your Laboratory Teaching Assistant will inform you when a report is due, and on which experiment you will report. Make sure that you have recorded all necessary information and data in your laboratory notebook to enable you to prepare a report on this experiment, if so directed, at some time in the future. Clemson University ECE Page 7 July 2010 Edition
Laboratory 3: DC Measurements Laboratory 3 DC Measurements Introduction: Voltage and current values may be used to determine the power consumed (or provided) by an electrical circuit. Electric power consumption is a very important factor in all electrical applications, ranging from portable computers to megawatt industrial complexes. Thus, an understanding of power and how it is measured is vital to all engineers. Objective: By the end of this lab, the student should know how to make DC measurements of voltages and currents to determine power dissipation/delivery for circuit elements, branches, and various combinations of elements and branches. Preparation: Read the introductory material in the ECE 2020 textbook describing the passive sign convention for circuit elements. Also, review the lab manual section Use of Laboratory Instruments. Prior to coming to lab class, calculate the values of voltage, current, and power absorbed/delivered for each circuit element in Figure 3.1 (i.e. do Part 0 of the Procedure). Also, sketch in your lab notebook the circuit diagrams to be used in each part of the procedure and have a table prepared for each part in order to record data. Equipment Needed: NI-ELVIS workstation. Resistors as required. Procedure: 0) For the circuit given in Figure 3.1, calculate the voltages across and currents through each circuit element. Using these values, determine the power absorbed or delivered by each circuit element. Include your calculations in your laboratory notebook. Record all of your theoretical results in a table for later comparison with your experimental values. Figure 3.1 - DC resistive network. Clemson University ECE Page 8 July 2010 Edition
Laboratory 3: DC Measurements 1) Set up the circuit in Figure 3.1. Adjust the output of the DC power supply to 10V and verify with the digital multimeter (DMM). Using the digital multimeter function in the NI-ELVIS workstation (set to measure DC Volts), measure the voltage across each individual circuit element. Before making each measurement, use the connection scheme shown in Figure 3.2 to verify that your voltmeter connection method is correct. Record the measurements in your laboratory notebook. For each measured voltage, determine the percent difference from the theoretical value determined in Part 0. Figure 3.2 - Connection scheme for circuit voltage measurements. 2) For the circuit in Figure 3.1, measure the current through each circuit element using the digital multimeter function in the NI-ELVIS workstation (set to measure DC Amps). Before each measurement, the circuit will have to be turned off and rewired to insert the ammeter in series with the component under test. Before making each measurement, use the connection scheme shown in Figure 3.3 to verify that your ammeter connection method is correct. Record the measurements in your laboratory notebook. For each measured current, determine the percent difference from the theoretical value determined in Part Ο. Figure 3.3 - Connection scheme for circuit current measurements. Clemson University ECE Page 9 July 2010 Edition
Laboratory 3: DC Measurements 3) Using your measurements from Parts 1 and 2, calculate the power absorbed or delivered by each circuit element. Record these values in your laboratory notebook. Compare them with the values obtained through circuit analysis in Part 0. Calculate the percent difference from the theoretical values. Probing Further: 1) What is the relationship between the power values obtained from your measured values of voltage and current and those calculated theoretically in Part 0? What do you think are sources of error? Explain. 2) How does the sum of power absorbed by the resistances in the circuit compare to the amount delivered by the source? Report: Your Laboratory Teaching Assistant will inform you when a report is due, and on which experiment you will report. Make sure that you have recorded all necessary information and data in your laboratory notebook to enable you to prepare a report on this experiment, if so directed, at some time in the future. Clemson University ECE Page 10 July 2010 Edition
Laboratory 4: Introduction to LT Spice Introduction: Laboratory 4 Introduction to LT Spice The widespread availability of computers has enabled the development of software which quite accurately models the behavior of electrical circuits. The most widely used program is SPICE, developed by the University of California-Berkeley in the mid-1970's and updated several times since then. Amongst the commercially available versions of SPICE is LT Spice from Beige Bag Software. LT Spice is loaded on the ECE 2110 laboratory computers, and a Lite version is available for free from the company (http://www.beigebag.com/adv4_lite.htm). As an introduction, you will learn to use LT Spice circuit simulation software with relatively simple circuits. Later, in the introductory electronics courses ECE 320 and ECE 321, you will learn to use LT Spice to simulate the operation of more advanced components such as diodes, transistors, and even a few integrated circuits. Objective: This lab should give the student a basic understanding of how to use LT Spice to simulate circuit operating conditions. After this lab, the student should be able to use LT Spice to solve or check basic circuit problems. Preparation: Prior to coming to lab class, calculate the voltages and currents for each resistor shown in the circuit of Figure 4.1 (i.e. do Part 0 of the Procedure). Equipment Needed: A computer with LT Spice loaded and ready to use. Clemson University ECE Page 11 July 2010 Edition
Laboratory 4: Introduction to LT Spice Procedure: 0) Before coming to lab, determine the voltages across and currents through each resistor in the circuit of Figure 4.1. Figure 4.1 - Resistive network for hand analysis and LT Spice simulation. 1) In the lab, your LTA will go through the guidelines for using computer equipment in a College of Engineering & Science laboratory. Then the LTA will provide an introduction to the LT Spice software environment. During this instruction session, you will learn how to: a) Open the software and create a new project. b) Place circuit components in your project workspace. c) Connect circuit components together. d) Set up circuit measurements. e) Change simulation execution settings. f) Run simulations. g) Display or export the simulation output. One important principal to keep in mind is that if you want LT Spice to display a graph or a table of something, you must include a suitable measurement device (e.g., voltmeter or ammeter) for that value. Anything without a meter won t be graphed. 2) Use LT Spice to solve for all of the resistor voltages and currents for the circuit of Figure 4.1. Your problem solutions, using LT Spice, are to be turned in. Compare your simulation measurements with the results of your calculations in Part 0. 3) Use LT Spice to simulate the circuit used in Laboratory 3 (Figure 3.1). Determine the voltages and currents for each circuit component. Your problem solutions, using LT Spice, are to be turned in. Clemson University ECE Page 12 July 2010 Edition
Laboratory 4: Introduction to LT Spice 4. Variability is inherent in any process, including the manufacture of resistors and capacitors. Such components are usually marked with a nominal (target) value and a tolerance within which the actual value might fall. R1 1000 10V V1 R2 510 R3 510 Figure 4.2: LT Spice representation of the circuit of Figure 3.1 Consider the circuit of Figure 4.2 the same circuit you simulated in Procedure 3 and measured in Laboratory 3. If the resistors you used in Laboratory 3 had a tolerance of 10%, their actual values might have been anywhere in the following ranges: 900Ω R1 1100Ω 459Ω R2 561Ω 459Ω R3 561Ω To understand how such variation might affect your measurements of current and voltage in an actual circuit, use LT Spice to calculate the currents and voltages if the resistors were at some of their extreme values, as indicated in the table below: R1 R2 R3 I1 I2 I3 V1 V2 1100 459 561 900 459 561 1100 459 459 900 459 459 (I1, I2, and I3 are the currents through R1, R2, and R3. V1 is the voltage across R1 and V2 is the voltage across R2 and R3.) Compare the voltages and currents of the last row (900Ω, 459Ω, and 459Ω) to the voltages and currents found in the simulation of Procedure 3 and explain your observations. For an understanding how the variability of a process is characterized by measurement of the mean, the variance, and the standard deviation of a parameter, read Appendix C, Fundamentals of Statistical Analysis in this manual. Probing Further: 1) How do the LT Spice simulation results in Part 1 compare to your calculations in Part 0? Can you account for any differences? Clemson University ECE Page 13 July 2010 Edition
Laboratory 4: Introduction to LT Spice 2) How do the LT Spice simulation results of Procedure 3 compare to your measurements in Laboratory 3? Can you account for any differences? Report: The problem solutions are due the next period. Include a title page and a brief procedure for each circuit. Report the results from LT Spice, and highlight these results on the printouts. Include a circuit diagram with each problem. Problem statements, files, and printouts should be included at the end of the report. Clemson University ECE Page 14 July 2010 Edition
Laboratory 5: Network Theorems I Laboratory 5 Network Theorems I Introduction: An understanding of the basic laws of electrical voltages and currents is essential to electrical engineering. Circuit analysis is dependent upon knowing the nature of the laws governing voltage and current characteristics. This lab studies Kirchhoff's Voltage Law, Kirchhoff's Current Law, voltage division, current division, and equivalent resistance. Objective: By the end of this lab, the student should understand KVL, KCL, voltage division, current division, and equivalent resistance combinations. Preparation: Read the material in the textbook that describes Kirchhoff's Voltage Law, Kirchhoff's Current Law, voltage division, current division, and equivalent resistance combinations. Be able to perform circuit calculations using these principles. Before coming to class, analyze each circuit and determine the theoretical values that should be obtained during the lab. Verify your calculations by performing LT Spice simulations for each circuit. Record both your calculations and simulation results in your laboratory notebook. Equipment Needed: NI-ELVIS workstation. Individual resistors as required. Resistance substitution box. Procedure: 1) Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the circuit as shown in Figure 6.1. Measure and record the total current into the circuit. Using the measured current and voltage, determine the equivalent resistance of the parallel components in the circuit. Replace the resistors with a resistance substitution box set to the equivalent resistance and measure the current as before. Compare the experimentally determined equivalent resistance to the theoretical value. Figure 6.1 - Determining parallel equivalent resistance. Clemson University ECE Page 15 July 2010 Edition
Laboratory 5: Network Theorems I 2) Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the voltage division circuit as shown in Figure 6.2. Begin with R = 510 Ω and measure the voltage across each resistor. Repeat with R = 1 kω, 2 kω, 3 kω, 4.3 kω, and 5.1 kω. Compare the measured voltages to those calculated using the voltage divider relation. Figure 6.2 - Effect of R on the component voltages. 3) Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the current division circuit as shown in Figure 6.3. Begin with R2 = 510 Ω and measure the currents I1, I2, and I3. Repeat with R2 = 1 kω, 2 kω, 3 kω, 4.3 kω, and 5.1 kω. Compare the measured currents to those calculated using equivalent circuit resistance and the current divider relation. Determine whether or not each set of measurements agrees with Kirchhoff's Current Law. Figure 6.3 - Sum of currents at a node. Clemson University ECE Page 16 July 2010 Edition
Laboratory 5: Network Theorems I 4) Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the circuit as shown in Figure 6.4. Measure the voltage across each component. Compare the measured voltages to those calculated using the voltage divider relation. Determine whether or not your measurements agree with Kirchhoff's Voltage Law. Figure 6.4 - Sum of voltages around a loop. 5) Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the circuit as shown in Figure 6.5. Measure the voltage across each component in loop 1. Repeat for loop 2 and loop 3. Compare your measured values with the terms in the KVL equation written for each loop. Determine whether or not your measurements agree with Kirchhoff's Voltage Law. Explain the reasons for any discrepancies found. Figure 6.5 - Sum of voltages around different loops. Clemson University ECE Page 17 July 2010 Edition
Laboratory 5: Network Theorems I Probing Further: 1) In part 2, what would the value of R have to be so that the voltage across R is 4/5 of the source voltage? Your answer should be quantitative (i.e. a number). 2) In part 3, what would the value of R2 have to be so that the current through R2 is 10 times the current through R3? Your answer should be quantitative. Report: Your Laboratory Teaching Assistant will inform you when a report is due and on which experiment you will report. Make sure that you have recorded all necessary information and data in your laboratory notebook to enable you to prepare a report on this experiment, if so directed, at some time in the future. Clemson University ECE Page 18 July 2010 Edition
Laboratory 6: Network Theorems II Laboratory 6 Network Theorems II Introduction: This lab focuses on the Thévenin equivalent and maximum power transfer theorems. Complex circuits are often replaced with their Thévenin equivalent to simplify analysis. For example, in the analysis of large industrial power systems the Thévenin equivalent is used in short circuit studies. Maximum power transfer is also an important concept which allows the designer to determine an optimal design when power is a constraint. Objective: By the end of this lab, the student should be able to verify Thévenin's equivalence theorem and the concept of maximum power transfer. Preparation: Read the material in the textbook that describes Thévenin's equivalence theorem and maximum power transfer. Equipment Needed: NI-ELVIS workstation. Individual resistors as required. Resistance substitution box. Procedure: 1) This part of the lab illustrates the use of Thévenin's theorem. Adjust the output of the DC power supply to 10V and verify with the digital multimeter. Set up the circuit as shown in Figure 7.1. Measure the open circuit voltage between nodes A and B. Measure the short circuit current between nodes A and B (i.e. connect the ammeter between nodes A and B). Using these measurements, determine the Thévenin equivalent circuit. Set up the newly determined Thévenin equivalent circuit and verify that this circuit has the same open circuit voltage and short circuit current as the previous circuit. Save this circuit for Part 2. Figure 7.1 - Determining the Thévenin equivalent circuit. Clemson University ECE Page 19 July 2010 Edition
Laboratory 6: Network Theorems II 2) This part of the lab is to illustrate maximum power transfer. Use the Thévenin equivalent circuit developed in Part 1. For a resistance substitution box R between nodes A and B, measure the current through and voltage across R if R = 0Ω. Repeat for R = 100Ω, 120Ω,..., 500Ω (in 20Ω increments). Determine the power dissipated by the resistor for each value of R. Plot power vs. resistance. At which value is the power a maximum? Probing Further: 1) Use LT Spice to determine the Thévenin equivalent for the circuit in Part 1. First, enter the circuit shown in Figure 7.1 using node B as the reference or "ground" node. The voltage at node A is then the open circuit voltage. To measure the short-circuit current between points A and B, place an ammeter between the points. Determine the Thévenin equivalent and compare to your experimentally obtained equivalent circuit in Part 1. Record your LT Spice programs and the data obtained from the simulation in your laboratory notebook by pasting in the printouts. Highlight the open-circuit voltage value and short-circuit current value obtained from the simulation. 2) Use LT Spice to simulate the circuit of Part 2. Start with the value of R = Rmax_pwr that you determined experimentally to give maximum power transfer and find, from the LT Spice simulation, the power delivered to this resistance. Then repeat with 20Ω increments through 100Ω (i.e. for Rmax_pwr 100Ω < R < Rmax_pwr + 100Ω). Compare the values of power obtained by simulation with those you obtained experimentally. Record your LT Spice programs and the data obtained from them in your laboratory notebook. Report: Your Laboratory Teaching Assistant will inform you when a report is due, and on which experiment you will report. Make sure that you have recorded all necessary information and data in your laboratory notebook to enable you to prepare a report on this experiment, if so directed, at some time in the future. Clemson University ECE Page 20 July 2010 Edition
Laboratory 7: The Oscilloscope Laboratory 7 The Oscilloscope Introduction: The digital oscilloscope allows the engineer to examine time varying waveforms in order to determine the magnitude, frequency, phase angle, and other waveform characteristics which depend upon the interaction of circuit elements with the sources driving them. Objective: By the end of the lab the student should be familiar with the controls of a digital oscilloscope and be able to use the instrument to observe periodic waveforms. Preparation: Review 'XYZs of Oscilloscopes', available at: www.tek.com (60+ pages). Be familiar with the following: voltage scaling (Volts/division), time base (seconds/division), input coupling, triggering, and measurement probes. Equipment Needed: NI-ELVIS workstation. Individual resistors as required. Procedure: 0) At the beginning of class, your LTA will review the virtual oscilloscope software used with the NI-ELVIS workstation. 1) Basic setup. Connect a cable with BNC fitting to the BNC jack for CH 0 of the oscilloscope on the left side of the NI-ELVIS II. Connect the cable s red lead to the FGEN output; connect the cable s black lead to GROUND. (Important note: Internally the oscilloscope s ground is connected to the NI-ELVIS circuit ground, therefore, the oscilloscope can only measure voltages across components that are connected to ground. Avoid grounding errors!) Set the function generator to output a 100Hz sine wave with amplitude = 3.0 VPP and DC offset = 0V. Open the oscilloscope window in the NI-ELVIS software. ENABLE the display for Channel 0. RUN the function generator and the oscilloscope. Turn on the measurement function for Channel 0 and record the measured values for RMS voltage, peak-to-peak voltage, and waveform frequency. Sketch the displayed waveform in your laboratory notebook. Compare your measurements with the expected values based on the function generator output. 2) Source control. Connect CH 0 to SYNC (adjacent to FGEN). Sketch this waveform in your laboratory notebook. Reconnect CH 0 to FGEN. Change the function generator output to a square wave, record the displayed waveform in your laboratory notebook, and measure the peak-to peak output voltage. Repeat this measurement for a triangular wave. Clemson University ECE Page 21 July 2010 Edition
Laboratory 7: The Oscilloscope 3) Voltage scaling. Reset the function generator to output a sine wave. Vary the vertical scale control for Channel 0 using either the control knob or pull-down menu. Record the effect that this control has on the displayed waveform. Set the control to 500mV/div and measure the peak-to-peak magnitude of the displayed waveform by counting (estimate) the number of peak-to-peak divisions and multiplying by the vertical scale. Compare this result with the measurement given by the oscilloscope. 4) Voltage offset manipulation. Vary the vertical position control in the oscilloscope and record the effects in your laboratory notebook, noting any changes in the measured RMS voltage. Return the offset to zero and add a DC offset of 0.5V to the function generator output. Record the effects in your laboratory notebook, noting any changes in the measured RMS voltage. 5) Time scaling. Return the DC offset in the function generator to 0V. Using either the timebase dial or pulldown menu, adjust the timebase of the oscilloscope display to the fastest setting (5μS/div). Record the effect that this setting has on the displayed measurements for the waveform. Gradually increase the timebase through each available setting until the slowest setting has been reached (200mS/div). Record the effect that this control has on the measurement of voltage and frequency. Return the timebase to a setting where 1-3 full cycles of the output sine wave is viewable. Set the Acquisition Mode to RUN ONCE and press RUN to capture a single sweep of the output waveform and measure the period of the waveform by counting (estimate) the number of time divisions for a single cycle and multiplying by the time scale. Compare this measurement to the inverse of the frequency measured by the oscilloscope. 6) Triggering / synch function. Return the screen update to 'RUN'. Adjust the triggering pulldown menu tο 'Edge' and record the oscilloscope response. Vary the function generator peak amplitude to verify that the oscilloscope is continuing to update the display in this mode of operation. 7) Cursor function. Set the function generator to output a 100Hz sine wave with peak amplitude = 3.0 VPP and DC offset = 0V. Return the triggering function to 'Immediate'. Display a single screen update of between 1-3 cycles of the output function. Switch the cursors function on and drag the cursors to appropriate points on the waveform to measure the period of the sine wave. Then adjust the cursors to measure the peak-to-peak voltage of the sine wave. Compare these measurements to those expected based on the function generator's output settings. 8) Connect the voltage divider circuit shown in Figure 8.1. Set the function generator to output a 1kHz sine wave with amplitude = 2VPP and DC offset = 0. Display the function generator output on Channel 0 of the oscilloscope and the voltage across the 100Ω resistor on Channel 1. Be careful to avoid grounding errors. Display and measure these voltages simultaneously. Measure the period of both waveforms using the cursor function. Sketch the waveforms in your laboratory notebook and record your settings for Volts/div and seconds/div. Compare your voltage measurements with theoretical calculations based on the voltage divider equation. Compare your waveform period measurement with the theoretical value obtained from the input frequency. Clemson University ECE Page 22 July 2010 Edition