How to measure a pulse signal on an oscilloscope

Written by j.t. barett
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How to measure a pulse signal on an oscilloscope
An oscilloscope can accurately measure pulse waveforms. (display of waveforms image by Albert Lozano from Fotolia.com)

A pulse signal is handy for evaluating both analogue and digital electronic circuits. Generally, a pulse begins at zero volts or ground, rises rapidly to a set voltage value, remains at that value for a brief period, then falls back to zero. An oscilloscope can capture the pulse, display it and measure its timing and voltage values. Because a pulse's rise and fall times are very fast, an oscilloscope must respond rapidly in order to render it accurately.

Skill level:
Moderate

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Things you need

  • Oscilloscope
  • Function generator
  • Coaxial test equipment cable with BNC connectors

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Instructions

  1. 1

    Connect one end of the BNC cable to the function generator's output. Connect the other end to the channel 1 input on the oscilloscope.

  2. 2

    Turn the function generator and oscilloscope on. Set the function generator's frequency to 1,000 Hz. Set its output waveform to a pulse. If it has a pulse width control, set it to between 10 and 30 per cent. Set its output amplitude to about 5 volts.

  3. 3

    Set the coupling mode on the oscilloscope input channel to DC. Set the vertical gain to 1 volt per division. Set the trigger source to channel 1. Set the horizontal sweep rate to 1 millisecond per division. You should see a series of pulse waveforms on the oscilloscope screen, along with the pulse's peak voltage value. If the pulses appear too high or low on the screen, adjust the vertical position control.

  4. 4

    Move the oscilloscope's left on-screen cursor to the horizontal point on the pulse where the voltage starts to rise from zero. Move the right cursor to the point where voltage returns to zero. The oscilloscope should measure and display the pulse's total "on" time on the screen.

  5. 5

    Move the oscilloscope's right cursor back to the point on the pulse where the voltage has attained its maximum value. The oscilloscope should measure and display the pulse's rise time on the screen.

  6. 6

    Return the right cursor to the point on the pulse where the voltage returns to zero. Move the left cursor to the last instant where the pulse is at its maximum voltage. The oscilloscope will measure and display the pulse's fall time.

  7. 7

    Using the menu buttons, find the oscilloscope's time statistics function. The screen will display the pulse's frequency and total time period.

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