Purpose: This lab is to (1) introduce to students National Instruments (NI) ELVIS (Educational Laboratory and Virtual Instrumentation Suite) II and Multisim as a tool for circuit design and testing, prototyping, and instrumentation; (2) create and simulate simple RLC circuits with Multisim, build the circuits on ELVIS II+, and test them with the built-in instruments multimeter and oscilloscope and; (3) establish the concept of and gain hands-on experience in signal processing by examining low-pass and high-pass filters.

Introduction

National Instruments (NI) ELVIS is a hands-on design and prototyping platform that integrates 12 most commonly used instruments, such as digital multimeter, oscilloscope, and function generator, into a compact form ideal for lab or classroom. NI ELVIS connects to a computer through USB connection, providing quick and easy acquisition and display of measurements. Based on NI LabVIEW graphical system design software, NI ELVIS offers the flexibility of virtual instrumentation and the ability of customizing your application.

Multisim is an industry-standard SPICE (Simulation Program with Integrated Circuits Emphasis) simulation environment, which helps students gain hands-on experience through practical application in designing, prototyping, and testing electrical circuits. The Multisim design approach saves prototype iterations and optimizes printed circuit board designs.

Multisim allows the use of multiple instruments, which means that the number of operating characteristics that may be monitored at the same time is unlimited. Because of that, students are able to observe the effects of changing a given component in every area of interest around the schematic.

Lab 4-3 Multisim, ELVIS II, and Basic Circuit – AC Circuit

The third section of Lab 4 aims at (1) introducing to students more virtual instruments in Multisim or those that are integrated into ELVIS II for circuit analysis and (2) gaining students more hands-on experiences with LabVIEW, Multisim, and ELVIS II. 

Pre-lab Assignment (25 pts in total):

1. Voltage gain or loss provides information about how an input signal is altered by the circuit for the amplitude (the vertical shift). When the amplitude of the output signal is larger than that of the input, it is called gain, otherwise, loss. Voltage gain or loss is defined as the ratio of the output voltage to the input voltage, or Vout/Vin, and is usually expressed with the logarithmic unit decibel (dB). What is the relationship between Vout/Vin and dB? Research and find the Vout/Vin and dB conversion equation and include it in your lab report (5 pts).
2. Phase shift (in degree) between the input and output provides information about how an input signal is altered by the circuit for the phase (the horizontal shift). Phase shift can be obtained by finding the time delay (i.e. the time difference between the input and output waveforms displayed on an oscilloscope) and then converting the time delay into phase shift. Research and find the phase shift/time delay conversion equation and include the equation in your lab report (5 pts).
3. What is the definition of cutoff frequency (i.e. corner frequency)? Research and find the answer and included a brief description of it in your own words in your lab report (5 pts).
4. Research bode plot for typical high pass filter; include a bode plot for typical high pass filter, of your own drawing or a figure from any source (cite if so), with the cutoff frequency marked on the plot, in your lab report (5 pts).
5. Research and find two circuit diagrams for typical active high-pass filter (non-inverting and without amplification) and passive-high pass filter; include the two circuit diagrams (cite the source) in your lab report (5 pts).

Exercise #1: Low-Pass Filter (75 pts in total):

1. Open “Exercise #1”. Double click on and open (if they are not opened) each of the instruments (Function Generator or XFG1, Oscilloscope or XSC1, and Bode Plotter or XBP2), Figure 1-0, so that you can set simulation conditions such as frequency and amplitude in the XFG1, run the circuit and visualize the input/output signal in the XSC1, and find the frequency and amplitude response of the circuit to the input in the XBP2.
   • For Function Generator or XFG1, only frequency and amplitude are needed to change for your exercises/assignments.
   • For Bode Plotter or XBP2, (1) both amplitude and phase of the output signal in relation to the input can be examined, under “Mode” and (2) the scale of x (frequency) and y (dB) axes can be adjusted under “Horizontal” and “Vertical”, respectively. For these simulations, use 1 Hz/100 kHz as the start/stop frequency for the “Magnitude” plot and 0 Deg./-100 Deg. as the upper/lower limit for the “Phase” plot.
   • For Oscilloscope or XSC1, you can change the x and y scale under “Timebase” and “Channel A”/“Channel B”, respectively, the input signal is displayed by “Channel A” in white and the output by “Channel B” in green (the color of the waveform can be changed by right clicking the wire in the circuit and select “Properties”“Net color”).
2. Assignment #1-1 (i.e. Table 1-1, 20 pts): Run the circuit with, (1) Vp = 5 V; (2) at the three designated frequencies and; (3) with the POT set at 90 %. Find the decibel (dB) values and Vout/Vin ratios from the Bode Plotter and the Oscilloscope, respectively. Report the values in Table 1-1 as your Multisim simulation data.
3. Assignment #1-2 (i.e. Table 1-2, 25 pts in total):
   • Add an NI ELVISmx Function Generator to the circuit, replace XFG1 with it, and connect it to the circuit as signal source. Add an NI ELVISmx Oscilloscope and an NI ELVISmx Bode Analyzer (all of them available from Multisim “NI ELVISmx Instrument” toolbar) to the circuit and connect them the same way as XSC1 and XBP2.
   • Run the circuit with the following settings, and find the decibel (dB) values and Vout/Vin ratios from the NI ELVISmx Bode Analyzer. Report the values in Table 1-2 as your Virtual ELVIS II measurement data.
   o NI ELVISmx Function Generator: Vpp = 10 V and at the same three designated frequencies;
   o NI ELVISmx Bode Analyzer: Start/Stop Frequency = 1 Hz/100 kHz and Steps = 50 (See Fig. 1-1 for details);
   o With the POT set at 90 %.
   • Assignment #1-3 (15 pts): Put a screenshot picture that includes the XBP2 “Magnitude” plot and “Phase” plot with the two plots from the NI ELVISmx Bode Analyzer, side by side and with cursors pointing at one same (closest to each other) frequency of your choice.
   • Assignment #1-4 (15 pts): Put a screenshot picture that includes the input and output on both XSC1 and the NI ELVISmx Oscilloscope for the simulation at Frequency = 900 Hz and with the SAME scales, i.e. “Timebase” and “Channel A”/“Channel B” in XSC1 vs. “Time/Div” and “Scale Volts/Div” for the both channels in the NI ELVISmx Oscilloscope.
   NOTES:
4. Shown in Fig. 1-2 is what the physical circuit looks like on an ELVIS. The two brown wires are not part of the circuit, but to be used to measure/adjust the resistance of the POT with the DMM with two selected pins, either 1 and 2 or 2 and 3, but not 1 and 3;
5. The two yellow arrows indicate which two pins of the POT are to be used for the referred resistance values;
6. There is a green ground wire at the very bottom of the picture.

Figure 1-0 Multisim simulation of a low-pass filter

Figure 1-1 Change step size (“Steps”) to acquire more data points; activate cursors (“Cursor Settings”) to find gain and phase information from the plots (indicated at the bottom of the graph as the cursors move along the plots).

Exercise #2: Active and Passive High-Pass Filter (25 pts in total): (- IGNORE)

1. Open “Exercise #2” and double click on each of the instruments (two Bode Plotters and two Oscilloscopes) to open four additional windows.
   • The upper portion of the circuit represents the active high-pass filter with an operational amplifier (op amp), while the lower portion of the circuit the passive.
   • Both filters are connected to a pair of bode plotter and oscilloscope, allowing to examine the filtering behaviors as well as input and output waveforms.
2. Assignment #2-1 (5 pts): Run this circuit at Frequency = 1052 Hz and amplitude = 1 Vrms. Put a screenshot picture of your results for the two XSC’s in your lab report.
   • rms stands for root mean square, 1 Vrms = 0.707 Vp = 0.3535 Vpp. The figure below shows their relationships (https://circuitdigest.com/calculators/rms-voltage-calculator).
3. Assignment #2-2: Find the dB values from both XBP’s at designated frequencies and fill in the “Multisim Simulation” column of Table 2 with these values. Find the cutoff frequency values for both filters from the Multisim simulations as well.
4. Assignment #2-3:
   • Build the circuit on ELVIS II (Figure 2). Run the circuit at Frequency = 1052 Hz and amplitude = 2.83 Vpp, and put a screenshot picture of your results (including those from both the Function Generator and Oscilloscope) in your lab report. The output waveform should look similar to the one you obtained from Multisim simulation.
   • Find the dB values from the built-in “Bode Analyzer” (Use Start Frequency = 1 Hz, Stop Frequency = 100 kHz, and 10 Steps/decade) for all the designated frequencies in the “ELVIS II Measurement” column of Table 2.
   • Find the cutoff frequency for both filters from the ELVIS measurements as well.

NOTES: (1) The red arrow in Figure 2 is where the left end of that green wire should actually go – the 4th hole from the top, NOT the 3rd, as ground. (2) The two white arrows are the power supply wires for the 741 CN operational amplifier (Op Amp), which connect with +15 V and -15 V, respectively, although they may not look so in the picture. The 741CN Op Amp pinouts shown below. (3) The circuit shown in Figure 2 is for measuring the active high-pass filter, with the op amp. For measuring the passive high-pass filter, you need to rewire. (4) The difference between the data from Multisim simulations and that from ELVIS II measurements for both the active and passive high-pass filters tells the difference between the virtual and physical instruments.

Figure 1-2 Circuit for “Exercise #1”

Figure 2 Circuit for “Exercise #2” (Active and passive high-pass filter)

Assignments (Report all values using 3 significant figures)

1. Table 1-1 for Assignment #1-1 (Multisim simulation) (20 pts)

Freq.
(Hz) POT (%) Amplitude Ratio (Vout/Vin) Phase Shift (degrees)
Bode Plotter
(dB** and Vout/Vin Ratio in %) Oscilloscope
(%) Bode Plotter Oscilloscope
5.1
( )*
90
—————– —————–
900
( )*
53 k
( )* —————– —————–

• Fill in with the actual frequency value read from Multisim Bode Plotter.
  ** dB values can be read from Multisim Bode Plotter directly and are required to report in this column and the Vout/Vin ratios in % can be converted from the dB values which are also required to report in this column as well. The voltage ratios reported in this column are to be compared with the voltage ratios obtained from Oscilloscope in the next column, both in %.

1. Table 1-2 for Assignment #1-2 (Virtual ELVIS II measurement) (25 pts)

Freq.
(Hz) POT (%) Amplitude Ratio (Vout/Vin) Phase Shift (degrees)
Bode Analyzer
(dB** and Vout/Vin Ratio in %) Oscilloscope
(%) Bode Analyzer Oscilloscope
5.1
( )* 90
( )# —————– —————–
900
( )* —————– —————–
53 k
( )* —————– —————–

• Fill in with the actual frequency value read from Bode Analyzer.
  ** Same as Table-1.

Fill in with the actual resistance value adjusted from the POT.

3. Table 2 for Assignment #2-2 and #2-3 (25 pts in total) (- IGNORE)

Freq.
(Hz) Multisim Simulation
(Bode Plotter) ELVIS II Measurement
(Bode Plotter)
Active/Passive
(dB) Phase Shift
Active/Passive (degrees) Active/Passive
(dB) Phase Shift
Active/Passive (degrees)
100
1.03 k
15.8 k
30.6 k
50.2 k
Cutoff Freq. ————— —————