ECE240L Exp 2 Formal Report

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California State University, Northridge *

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240

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Electrical Engineering

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Apr 3, 2024

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Gregory Nalbandian Nicholas Fanderlik Wednesdays 2:00 pm - 4:45 pm September 27th, 2023 ECE 240 Lab Experiment 2: Oscilloscopes

Page 2 Objective: The purpose of this lab experiment is to understand the importance of oscilloscopes and function generators. An oscilloscope can show the fluctuations in a circuit’s voltage in the form of a live graph, providing a more accurate visual representation than a DMM. The function generator is used as a source for the circuit created in this experiment in the form of both Sine and Square waves. Components: The components in this experiment include the following: one 4.7k ohm resistor, one 10k ohm resistor, three BNC-to-alligator clip connectors, one BNC-to-BNC wire, and two 24-inch banana plugs. Equipment: The equipment used includes the following: Agilent Technologies DSO1002A Oscilloscope(60MHz - 2GSa/s), Agilent Technologies 33220A 20MHz Function / Arbitrary Waveform Generator, Tektronix CDM250 Digital Multimeter, and WB-104-1 Breadboard. Theory: Oscilloscopes provide live readings of voltage in a circuit in the form of a wave. The y-axis displays the voltage, or amplitude of the graph, while the x-axis represents the time, which can be used to determine the frequency of the graph. The various knobs and buttons found on the face of the oscilloscope can be used to adjust the picture or the graph, allowing a more accurate and clearer observation. Procedure: 1. Turn on both the digital function generator and the digital oscilloscope 2. Connect the BNC-to-BNC cable to the output port on the function generator to the channel 1 port on the oscilloscope 3. For the function generator, set the frequency setting to 1kHz, volt peak-to-peak to 4 volts, and press the sine button 4. The oscilloscope’s voltage sensitivity should be set to 5V/DIV 5. Sketch the display of the oscilloscope after setting the time base to 1ms/div, 0.1ms/div, and 10µs/div. Label both axes with the corresponding divisions 6. Set the scale of the oscilloscope to where two cycles of the sine wave can be observed, and measure its period. Then, calculate the frequency of the wave 7. Calculate the percentage error between the measured and expected values of the frequency using the equation found in the lab manual 8. Measure the voltage of the sine wave by connecting the function generator output to the AC input of the DMM. Record the RMS measurement of the sine wave’s voltage

Page 3 9. Using the RMS measured in the previous step, calculate the factor K using the formula: K = V_peak / V_RMS 10. Repeat all previous steps but with the square wave function 11. Construct the circuit shown in the lab manual for experiment 2 12. Sketch the graph shown on the oscilloscope’s display. Connect the VS to channel 1 and VL to channel 2 13. Change the setting to X-Y on the oscilloscope and calculate the slope of the graph 14. Calculate the theoretical value of the slope. Data: Figure 1: Circuit Diagram for Experiment 2

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Page 4 Figure 2: Sketch of Sine Graphs at 1ms/div, 0.1ms/div, and 10µs/div respectively Table 1: Period, Calculated Frequency, and %error of Frequency from observed sine wave(2 cycles displayed on oscilloscope) Measured Period (ms) 1.04 Expected Period (ms) 1.00 Measured Frequency (kHz) 0.9615 Expected Frequency (kHz) 1.00 % Error 3.80% Voltage Recorded by DMM: 1.38V RMS

Page 5 Calculations for Sine Wave: R_eq = R1 + R2 = 10 kΩ + 4.7 kΩ = 14.7 kΩ %error = ( (f_measured - f_expected) / (f_expected) ) x 100% = (0.9615 - 1) / 1 *100 = 3.8% K = Vpeak / VRMS = 2V / 1.38V = 1.45 Figure 3: Sketch of Square Graphs at 1ms/div, 0.1ms/div, and 10µs/div respectively Table 2: Period, Calculated Frequency, and %error of Frequency from observed Square wave(2 cycles displayed on oscilloscope) Measured Period (ms) 1.00 Expected Period (ms) 1.00 Measured Frequency (kHz) 1.00 Expected Frequency (kHz) 1.00 % Error 0% Voltage Recorded by DMM: 2.13 V RMS

Page 6 %error = ( (f_measured - f_expected) / (f_expected) ) x 100% = (1 - 1) / 1 *100 = 0% K = Vpeak / VRMS = 2V / 2.13V = 0.943 Figure 4: Sketch of X-Y Display of Square Wave Used To Calculate Slope Theoretical value m = VL / VS = 1 / 3 = 0.33 Discussion: We gleaned valuable insights from both the initial and subsequent segments of the experiment, which illustrated how varying time intervals affect the appearance of a sine wave and a square wave with the same frequency. Time bases of 1ms/div and 0.1ms/div proved suitable for visualizing the waveforms, whereas a time base of 10μs/div was too brief to discern a waveform. Additionally, we acquired the ability to determine the period by adjusting the time base to display two cycles of the sine wave. We conducted frequency calculations and computed the percentage error between our measured frequency and the function generator's preset frequency, resulting in a 3.8% error, but the square wave resulted in 0% because our measured frequency matched the function generator's setting precisely. Subsequently, we proceeded to measure the voltages V_L and V_S in our constructed circuit(Figure 1). Utilizing the oscilloscope's X-Y graphing feature, we generated a graph and

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Page 7 measured its slope. This process was straightforward in terms of data interpretation and slope calculation. Conclusion: In conclusion, oscilloscopes are indispensable instruments for accurately measuring signal voltages. Within the scope of our experiment, we made efficient use of oscilloscopes to ascertain a range of parameters, such as peak voltage, oscillation period, and frequency. The data we obtained was highly legible, frequently yielding an insignificant 0.0% margin of error. This experimental endeavor not only furnished us with precise information but also granted us a clear and comprehensive understanding of the interactions between analog electrical currents, voltage levels, and frequencies. Consequently, it contributed significantly to our comprehension of these fundamental principles within the field of electrical engineering.