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Lab #9 AC Circuits

• Activity #1 – Simulating a Low Pass Circuit

• Activity #2 – Building & Testing a Low Pass Circuit

• Activity #3 – Comparison of 3 methods

• Activity #4 – Simulation of a High Pass Circuit

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Phase Angle MeasurementUsing the Oscilloscope

• This procedure measures the phase angle difference between two sinusoidal waveforms connected to channels A and B of the scope.

• The leading waveform should be connected to channel A of the scope.

• The “leading” waveform does things (like reaching a peak value or passing through zero in a specific direction) earlier than the “lagging” waveform does them.

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For the waveforms shown, waveform B lags waveform A by 39°. This can also be stated as waveform A leads waveform B by 39°.

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2. Adjust the FOCUS and INTENSITY to obtain a clear, readable display.

1. Turn on Power

4. If you don’t want the screen text on, repeatedly press this button until it turns off

3. If DIGITAL MEMORY is not displayed, press this button

Procedure

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5. Make sure all three VAR knobs are in the CAL position

6. Set the TRIG LEVEL knob to near mid-range (pointing upward).

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7. Press the GND buttons on channels A and B to disconnect the input signals and “ground” the channels (zero voltage).

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8. Adjust the Y POS knobs for channels A and B until both traces line up with the center horizontal grid line. Do not change these controls at any other time.

9. If necessary, adjust the X POS knob to start the traces at the left side of the grid

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10. Press both GND buttons to reconnect and display the waveforms.

11. Press the green AUTO SET button to initialize the scope settings.

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12. Adjust the channel A and B voltage controls to display the tallest waveforms possible while keeping the waveforms on the screen. Do not change the Y POS settings.

13. Adjust the TB (time base) and TRIG LEVEL controls so that slightly more than one full cycle (period) at the zero crossings is displayed for both waveforms

14. Press this button to turn on the screen text.

One Cycle

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15. Press this button to turn on the cursors

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16. Press this button to allow control of the time cursors for measuring X or horizontal distances.

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17. Use these two buttons to position the left cursor at the point that the A trace passes through zero (center horizontal grid line) with an upward slope.

18. To measure the period and frequency, use these two buttons to position the right cursor at the point that the A trace passes through zero (center horizontal grid line) with an upward slope.

19. Press the RETURN button

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Note the display of the period and frequency of the waveform (as measured by the cursors)

20. Press the MODE button to change to phase in radians or degrees.

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21. Repeatedly press this button until PH (phase) is highlighted and the measurement at the top of the screen changes to Δt = 360°

22. Press the RETURN button to begin to measure phase difference

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23. Press the T-CTRL button

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24. Use these two buttons to position the right cursor at the point that the B trace first passes through zero (center horizontal grid line) with an upward slope.

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25. The cursor measurement displayed at the top of the screen is the phase angle difference between the channel A and B waveforms. In the example shown, waveform B lags waveform A by 39.0 degrees.