How to Create a Bode Plot

Step-by-Step Guide

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   Step 1: Check that the function generator and oscilloscope are connected to the closest AC outlet.

   a. Connect the red positive lead to the input terminal of your circuit. b. Connect the black negative lead to the ground terminal of your circuit. , a. Connect the red positive lead to the input terminal of your circuit. b. Connect the black negative lead to the ground terminal of your circuit. , a. Connect the red positive lead to the output terminal of your circuit. b.
   
   Connect the black negative lead to the ground terminal of your circuit, (unless instructed otherwise by the lab TA). ,, They should be as shown in Figure
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   Figure 1 – Your equipment connections ,,,,  The light above the button turns on.  Your screen should look similar to the Figure shown in this step. ,  This can be done with the large dial on the function generator, or with the four soft-keys below the display.  The buttons marked “- val +” change the digit under the cursor, and the “< cur >” buttons move the cursor.,  The light above the button turns on.  Your screen should look similar to Figure 5 now.,  Notice that this is Vpp, the peak-to-peak voltage.
   
   The maximum (positive) and minimum (negative) voltages of the wave will be half the peak-to-peak voltage., The light to the left of the button turns on. ,  Its display should look similar to Figure
   6.  The wave may appear on the display, or it may only show noise. The next steps will bring it into focus., Its display should look similar to Figure 7, and the waves should appear in focus., This tells the oscilloscope to display a single period of the wave. Your display should look like the one in Figure
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   The oscilloscope soft-keys are located to the right of the display. ,  The default measurement screen will be shown, like the one in Figure
   8.,  Press the top soft-key labeled “Source” until “CH1” is listed.  Press the second soft-key from the top labeled “Type” until “Freq” is shown.  Your display should look like the one in Figure
   9.  Press the bottom soft-key to go back.,  Press the top soft-key labeled “Source” until “CH1” is listed.  Press the second soft-key from the top labeled “Type” until “Pk-Pk” is shown.  Your display should look like the one in Figure
   10.  Press the bottom soft-key to go back.,  Press the top soft-key labeled “Source” until “CH2” is listed.  Press the second soft-key from the top labeled “Type” until “Freq” is shown. Your display should look like the one in Figure
   11.  Press the last soft-key (fifth from the top) to go back., Press the top soft-key labeled “Source” until “CH2” is listed. Press the second soft-key from the top labeled “Type” until “Pk-Pk” is shown. Your display should look like the one in Figure
   12.  Press the bottom soft-key to go back.,  Your display should now show more than one period, like the display in Figure
   13.  The CH1 and CH2 frequency measurements should change from “?” to the true reading.,  The default screen should look like the one in Figure
   14.,  The middle of the right column of the screen shows us the readings we are interested in:  Δt and ΔV.  Below that, the readings for Cursor 1 and Cursor 2 are shown.,  Label the columns “Frequency,” “Vin,” “dV,” “Vout,” “Delay,” “Phase” and “Gain.”,,, The “=B2+C2” turns into a zero since we haven’t entered anything into B2 or C2.,  The formula gets copied from D2 into D3, with Excel changing its formula into “=B3+C3” automatically.  Keep pressing Ctrl+D then return until you fill the column for each of your frequencies.,,  Press Ctrl+D, then return as you did before to fill the column.,,  Press Ctrl+D, then return as you did before to fill the column.  Ignore the errors for now.,  You can use it the next time you need to create a Bode plot, letting you skip Part
   6.,  If it isn’t, press the “CURSOR” button on the top middle of the oscilloscope.     ,,,  The knob is unlabeled and is located just above the “PRINT” button.,,,  Position the cursor so that it lines up with the very top of the CH2 (lower, in blue) wave.,, Select the Frequency and Gain columns.,,,,,,,,,
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   Step 2: Connect the first probe to the “50 Ω OUTPUT” connector on the front lower-right corner of the function generator.

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   Step 3: Connect the second probe to the “CH 1” connector on the front of the oscilloscope.

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   Step 4: Connect the third probe to the “CH 2” connector on the front of the oscilloscope.

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   Step 5: Make sure that the cables are not hanging over the edge of the workspace.

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   Step 6: Double-check the connections.

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   Step 7: Press the power button (labeled “O/I”) on the top side of the oscilloscope.

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   Step 8: Press the “POWER” button on the front upper-right corner of the function generator.

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   Step 9: After the equipment performs its self-test

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    Step 10: it should look similar to what’s shown in Figure 2 (shown in this step).

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    Step 11: Press the button below “FREQ.” on the function generator.

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    Step 12: Adjust the frequency to the lowest frequency you wish to test

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    Step 13: your starting frequency.

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    Step 14: Press the button below “AMPL.” on the function generator.

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    Step 15: Adjust the amplitude to the voltage specified in the lab procedure for the circuit being tested

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    Step 16: using the same dial or soft-keys.

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    Step 17: Press the button “OUTPUT” on the function generator.

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    Step 18: Press the “DEFAULT SETUP” button on the upper-right corner of the oscilloscope.

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    Step 19: Press the “AUTOSET” button on the upper-right corner of the oscilloscope.

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    Step 20: Press the second soft-key from the top.

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    Step 21: Press the “MEASURE” button on the top middle of the oscilloscope.

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    Step 22: Press the top soft-key on the oscilloscope to select the first measurement.

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    Step 23: Press the second soft-key from the top to select the second measurement.

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    Step 24:   Press the third soft-key from the top to select the third measurement.

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    Step 25: Press the fourth soft-key from the top to select the fourth measurement.

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    Step 26: Turn the “HORIZONTAL SEC/DIV” knob counterclockwise a little until it clicks once.

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    Step 27: Press the “CURSOR” button on the top middle of the oscilloscope.

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    Step 28: Press the top soft-key next to “Type” until “Time” is listed.

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    Step 29: On your lab computer

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    Step 30: open Excel and start a new spreadsheet.

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    Step 31: Below “Frequency

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    Step 32: ” enter each frequency you plan to test (refer to your lab procedures).

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    Step 33: Below “Vout” in cell D2

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    Step 34: enter this formula:  =B2+C2

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    Step 35: Press return.

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    Step 36: Press Ctrl+D

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    Step 37: then return.

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    Step 38: Below “Phase” in cell F2

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    Step 39: enter this formula:  =2*pi()*A2*E2

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    Step 40: Press return.

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    Step 41: Below “Gain” in cell G2

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    Step 42: enter this formula:  =20*log10(D2/B2)

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    Step 43: Press return.

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    Step 44: Save this worksheet to use as a template.

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    Step 45: Your oscilloscope should still be on the cursor display from the end of Part 5.

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    Step 46: Turn the “HORIZONTAL SEC/DIV” knob to zoom in on the wave

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    Step 47: so that a single period is shown.

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    Step 48: Push the fourth soft-key from the top to select Cursor 1.

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    Step 49: Turn the “multi-function” knob located on the center top of the oscilloscope to move the cursor.

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    Step 50: Position the cursor so that it lines up with the very top of the CH1 (upper

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    Step 51: in orange) wave.

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    Step 52: Push the last soft-key (fifth from the top) to select Cursor 2.

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    Step 53: Turn the “multi-function” knob located on the center top of the oscilloscope to move the cursor.

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    Step 54: On your spreadsheet

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    Step 55: record your data: a. Vin – the voltage reading under Cursor 1 (820 mV in the example above; record this as 0.820 in your spreadsheet) b. dV – the reading next to ΔV (20.0 mV in the example above; record this as 0.020 in your spreadsheet) c. Delay – the reading next to Δt (160.0 µs in the example above; record this as 0.000160 in your spreadsheet).

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    Step 56: For the Gain plot: Enter one step here and then click 1.

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    Step 57: Click “Insert” and look for the “Scatter Chart” option.

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    Step 58: Right-click the vertical axis and choose “Format Axis…”

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    Step 59: Click “Logarithmic scale”

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    Step 60: Right-click the horizontal axis and choose “Format Axis…”

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    Step 61: Click “Logarithmic scale”

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    Step 62: For the Phase plot: Select the Frequency and Gain columns.

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    Step 63: Enter one step here and then click “Insert” and look for the “Scatter Chart” option.

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    Step 64: Right-click the horizontal axis and choose “Format Axis…”

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    Step 65: Click “Logarithmic scale”.

Detailed Guide

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