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Apr 3, 2024

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ECE 115 – Spring 2022 Experiment #5 Circle Lab Section: M11 Tu8 Tu2 W11 Name (print): UIN: Signature: By signing, I attest that the document submitted is my own original work.
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago Introduction This experiment will introduce you to the use of the oscilloscope and the function generator We will also use the circuit simulator that we used in the last few experiments to determine a set of expected results. The experimental results will then be used to verify the simulation results. To be adequately prepared for this experiment, it is important that you consult the following items: Oscilloscope document in the Lab Equipment section of Blackboard Function Generator document in the Lab Equipment section of Blackboard Experiment #5 Introductory Video Purpose The purpose of this experiment is to introduce and familiarize you with some additional lab equipment that is often used in bench measurements of electrical circuits. These new pieces of equipment that you will use in this experiment are the oscilloscope and the function generator. After you have completed this experiment, you will know how to: construct a circuit using the breadboard, wires, resistors, capacitors use the multimeter to measure resistances use the function generator to setup a test voltage use the oscilloscope to view and measure voltage waveforms validate the measurements by comparing with simulation results Software/Documents/Parts/Equipment used in Experiment LTspice simulation software by Analog Devices Inc. Resistors and capacitors from the lab kit; wires, cables, breadboard, multimeter, oscilloscope, function generator. Resistor color code and Equipment Overview documents in Blackboard. Theory In this experiment, you will be using parts from your lab kit and equipment located in the ECE 115 lab in 3250 SEL (Science and Engineering Laboratories, East). You will also be using the LTspice software that is installed on the laboratory computers. It is essential that you are familiar with the procedures developed in the previous experiments as we will build upon them as we move forward with the experiments. To be adequately prepared for this experiment, it is important that you watch the Experiment #5 Introduc- tory Video and be familiar with the simulation software LTspice. As mentioned previously, we will be using two new pieces of equipment in this experiment: oscilloscope, function generator. Oscilloscope – refer to the document in the Lab Equipment section on Blackboard The oscilloscope (also referred to as scope), is probably the most widely used instrument to investigate the operation of an electronic circuit. The oscilloscope provides a visual display of the voltage between two points in an electronic circuit, as this voltage varies with time. This oscilloscope in our laboratory can display two voltages simultaneously, one voltage that is an input to its channel 1 input and another voltage that is an input to its channel 2 input. The two inputs are located to the right of and below the display screen. Each scope input will have adapters that have two terminals – the black terminal is called the ground input terminal, and the red terminal is the positive input terminal. 1 of 9
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago The user can elect to view either channel 1 or channel 2, or both, or the difference between the channel 1 and 2 input voltages. There are many attributes of how the observed wave shape should appear on the display, and that is why there are many controls on the front panel of a scope. Some of these controls are set according to user preferences, such as: the horizontal width of the displayed image, the vertical position of the displayed wave shape, the intensity (brightness) of the display, and others. Some of these controls are set according to the displayed voltage attributes. The most used controls are the ones that control the horizontal and vertical settings – these basically allow you to see more or less of the waveform in the horizontal (time) and vertical (voltage) axes. The horizontal time scales are in seconds/division and the vertical voltage scales are in volts/division – where the divisions are the sections of the display. You can think of the display as a piece of graph paper and the horizontal and vertical control allow you to changes the spacing of the major divisions. Function Generator – refer to the document in the Lab Equipment section on Blackboard The function (or signal) generator is an instrument that produces a voltage having a wave shape that is one of a set of standard wave shapes. Some standard wave shapes are: sinusoidal, triangular and square. Its purpose is to provide a controlled voltage signal that can be inputted into an electronic circuit to investigate how the circuit will respond to inputs, when the input properties are known and can be controlled. The signal generator output voltage properties that can be set are amplitude and frequency for sinusoidal, triangular and square waves. In this experiment we will use the function generator to apply a sinusoidal voltage waveform with certain amplitude and frequency. This voltage waveform will the be source voltage that will be applied to a circuit that we will further investigate. 2 of 9
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ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago Procedure In the first part of the experiment, we will simulate one of the circuits that we will eventually construct and test. We will start with the sample circuit file exp5-circuit1.asc that has already been placed in Blackboard under the Experiment #5 material. Save the LTspice circuit file exp5-circuit1.asc into the ECE115 folder on your desktop. Navigate to the ECE115 directory and double-click on exp5-circuit1.asc . This should automatically launch LTspice with the circuit file loaded. Alternatively, you can start LTspice from the desktop icon and use the menu item File > Open... and navigate to the ECE115 directory to launch the file. Circuit #1 exp5-circuit1.asc 5V 1kHz sine v in ( t ) 22kΩ 10kΩ R 1 R 2 in out Before proceeding with the simulation, you should note that the general form of the LTspice sinewave is v s ( t ) = A sin(2 πft ) + B , where A is the amplitude, f is the frequency (number of cycles per second) and B is the offset. In LTspice, the command for the sinewave has the form SINE(B A f) . In our simulation we have a 5V, 1kHz sinewave with zero offset so the command that accomplishes it is SINE(0 5 1k) . With a frequency of 1kHz, the waveform will have 1000 sinewave cycles per second. This means that the duration of each period T = 1 /f = 1 / 1000 = 0 . 001s = 1ms, or 1 milliseconds. The input voltage can be given as v in = 5 sin(2 π 1000 t ). With the circuit shown above ( exp5-circuit1.asc ) opened in LTspice, you will see that the sinewave source is already setup and we are ready to simulate the circuit for 3 cycles or 3 ms. The command .tran 3m that you see will run the transient (time) analysis for 5ms. Using the information from the Experiment #5 Introductory Video do the following: 1. Run the transient (time) simulation by clicking on the “running man” and probe (display) node voltages v in and v out marked as in and out , respectively. Carefully sketch these waveforms on the grid, noting the horizontal time and vertical voltage markings. 3 of 9
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago 2. Based on voltage division, determine a general expression for v out as a function of v in , R 1 and R 2 . If you use the numerical values of the resistors, do the waveforms from the simulation match what is expected from voltage division? 3. Now we will setup this circuit using the waveform (function) generator and resistors and then we will measure the input and output voltages using the oscilloscope. First, let’s setup the input voltage (5V, 1kHz sinewave). Power up the function generator and the oscilloscope, and use a cable to connect the output of the function generator to Channel 1 input of the oscilloscope. Your TA should explain to you which cables to use and how to make the connections . Set the generator to produce a sinusoidal voltage having a 1 kHz frequency and 5V amplitude. The front panel of the oscilloscope has knobs and buttons. The buttons bring up softkey menus. Select Channel 1 for display. Note: You can help with the built-in help system by pressing and holding any button . 4. The oscilloscope has an autoscale feature that automatically sets up the oscilloscope to best display the input. Simply press the Autoscale button and you should see your waveform being displayed. Once you have the input voltage setup as desired, go to the next step. 5. From your kit, find the 10kΩ (brown-black-orange) and the 22kΩ (red-red-orange) resistors and measure their actual resistance values by using the multimeter and recording the values below. R 1 = R 2 = 6. Now we are ready to build the circuit with the two resistors and the sinusoidal input voltage source. First place the two resistors on the breadboard. Then connect the output of the function generator to the breadboard red and black terminals. The circuit should now be functional and realize the circuit that we have simulated. 7. Now we are ready to make the connections to display the voltages on the oscilloscope. Using cables with connectors at one end and clips on the other, make connections from the circuit to the oscilloscope to measure the input voltage v in on Channel 1 and output voltage v out on Channel 2. The diagram below will guide you in making the connections. 4 of 9
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago 5V 1kHz sine v in ( t ) 22kΩ 10kΩ R 1 R 2 in out (+) red terminal (+) red terminal (-) black terminal (-) black terminal Channel 1 Channel 1 Channel 2 Channel 2 8. By using the channel settings, display both Channel 1 and Channel 2 voltages. These correspond to node voltages v in and v out . Now carefully sketch these waveforms, noting the horizontal time and vertical voltage spacing. In particular, please note the vertical (voltage/division) and horizontal (time/division) settings. 9. Based on the oscilloscope waveforms and voltage and time division settings, how do the measured wave- forms compare with the simulated waveforms. 5 of 9
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ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago In the second part of the experiment, we will simulate circuit file exp5-circuit2.asc that has already been placed in Blackboard under the Experiment #5 material. 10. Save the LTspice circuit file exp5-circuit2.asc into the ECE115 folder on your desktop. 11. Navigate to the ECE115 directory and double-click on exp5-circuit2.asc . This should automatically launch LTspice with the circuit file loaded. Alternatively, you can start LTspice from the desktop icon and use the menu item File > Open... and navigate to the ECE115 directory to launch the file. Circuit #2 exp5-circuit2.asc 5V 1kHz sine v in ( t ) 22kΩ 10kΩ 0 . 1 μ F C 1 R 1 R 2 in out This is basically the same circuit as before but we have added a capacitor C 1 = 0 . 1 μ F across R 2 . 12. Run the transient (time) simulation by clicking on the “running man” and probe (display) node voltages v in and v out marked as in and out , respectively. Carefully sketch these waveforms, noting the horizontal time and vertical voltage markings. 13. Now we will setup this circuit on the breadboard by adding the capacitor to the breadboard. From your kit, find the 0 . 1 μ F capacitor and place it across the R 2 = 22kΩ resistor. The capacitor is pretty small and orange in color – it should be located in the bag with your other capacitors that look like small blue cans. 6 of 9
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago 14. With all of the connections in tact from the previous circuit, you should be able to see the new waveforms for the input and output voltages, v in and v out . Now carefully sketch these waveforms, noting the horizontal time and vertical voltage spacing. In particular, please note the vertical (voltage/division) and horizontal (time/division) settings. 15. Based on the oscilloscope waveforms and voltage and time division settings, how do the measured waveforms compare with the simulated waveforms. 7 of 9
ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago In the third part of the experiment, you will modify the circuit file exp5-circuit2.asc by changing one of the resistor values. 16. Start with the LTspice circuit file exp5-circuit2.asc from the last section and change the R 1 from a 10kΩ to a 1kΩ resistor (as shown below) and save the new file under the name exp5-circuit3.asc to the ECE115 using the menu item File > Save As... . Circuit #3 exp5-circuit3.asc 5V 1kHz sine v in ( t ) 22kΩ 1kΩ 0 . 1 μ F C 1 R 1 R 2 in out 17. Run the transient (time) simulation by clicking on the “running man” and probe (display) node voltages v in and v out marked as in and out , respectively. Carefully sketch these waveforms, noting the horizontal time and vertical voltage markings. 18. Now we will setup this circuit on the breadboard by changing R 1 from a 10kΩ to a 1kΩ resistor. Remove the 10kΩ resistor. From your kit, find the 1kΩ (brown-black-red) resistor and place it on the breadboard. 8 of 9
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ECE 115 Intro. to Electrical and Computer Engineering Experiment #5 – Using the Oscilloscope and the Function Generator University of Illinois at Chicago 19. With all of the connections in tact from the previous circuit, you should be able to see the new waveforms for the input and output voltages, v in and v out . Now carefully sketch these waveforms, noting the horizontal time and vertical voltage spacing. In particular, please note the vertical (voltage/division) and horizontal (time/division) settings. 20. Based on the oscilloscope waveforms and voltage and time division settings, how do the measured waveforms compare with the simulated waveforms. Questions Comment on the comparison of simulation results and oscilloscope measurements. Are the simulations good estimates of what you actually measured? 9 of 9