Nassau Community College
Electronics and Telecommunications
Performing Phase Measurements:
A common time measurement performed with the oscilloscope is a
measurement of the phase angle between two waveforms. The traces on the
oscilloscope must be properly set up. Then the phase angle may be
determined using information from the display.
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
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. This must be done
for both channels.
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. Set the vertical amplifier coupling switch (AC-GND-DC) to GND on
each channel. This will result in a horizontal line for each channel
5. Using the vertical position control for each channel, position the two lines on the center graticule line.
6. Switch both vertical amplifier coupling switches (AC-GND-DC) to AC. This results in both traces being seen.
7. Use the horizontal position control to position one of the traces at an intersection of the graticule lines.
The formula used to calculate phase angle is:
1. Count the number of horizontal divisions from the where the trace
crosses the intersection point to where the other waveform crosses the
center graticule line. This is t
2. Measure the period of one of the waves. This is T.
3. The phase angle is:
Be sure to record which wave is leading.