Nassau Community College
Electronics and Telecommunications
Reference Sheet

Oscilloscope Time Measurement

 

Performing Time Measurements:

The most common time measurement performed with the oscilloscope is a measurement of a waveform’s period. The trace on the oscilloscope must be properly set up. Then the period may be determined using information from the display and horizontal (time base) control settings.

Setting Up The Waveform Display:

  1. Begin by setting the vertical amplifier coupling switch (AC-GND-DC) to AC. This will block the DC on the signal, making it easier to center the trace.
  2. Adjust the vertical amplifier VOLTS/DIV control to get the largest possible display on the screen. It may be necessary to adjust the vertical amplifier POSITION control to center the trace as you do this. Be sure the red CAL knob is in the detent position.
  3. Adjust the horizontal time base SEC/DIV to get about one cycle of the waveform on the display. You must have at least one complete cycle, but as few cycles as possible to maximize accuracy.
  4. Using the horizontal time base POSITION control, adjust the trace to cross the center horizontal graticule line at a vertical graticule line, as shown below. You are now ready to make a period measurement.



Measuring Period:

  1. Count the number of horizontal divisions from the where the trace crosses the center horizontal graticule line to where it crosses again with the same slope, as shown below. Remember a minor division is 0.2 divisions.

  2. Determine the value of each division from the horizontal time base SEC/DIV control.
  3. The period (T) is:

    T = DIV x SEC/DIV