APPLICATION
PHASE DIFFERENCE MEASUREMENTS
This procedure is useful in measuring the phase difference of
signals of the same frequency.
1.
Apply the two signals to the CH1 and CH2 INPUTS,
setting the V MODE to DUAL and choosing either
CHOP or ALT mode.
2.
Set the SOURCE to the signal which is leading in phase
and use VOLTS/DIV to adjust the signals such that they
are equal in amplitude. Adjust the other controls for a
normal display.
3. Use SWEEP TIME/DIV and A VAR to adjust the display
such that one cycle of the signals occupies 8 divisions
of horizontal display.
Use the r POSITION to bring the signals in the center
of the screen.
Having set up the display as above, one division now
represents 45° .in phase.
4.
Measure the horizontal distance between corresponding
points on the two waveforms.
Using the formula:
Phase difference = horizontal distance (div) x 45°/div
Phase difference = horizontal distance of new sweep range
(div) x45°/div
New SWEEP TIME/DIV setting
Original SWEEP TIME/DIV setting
Another simple method of obtaining more accuracy quickly
is to simply use x 10 MAG for a scale of 1 division =
45°/div
One cycle adjusted to occupy 8 div.
Expanded sweep waveform display.
[EXAMPLE]
For the example, the horizontal distance is 1.7 divisions.
Substituting the given value:
The phase difference = 1.7 (div) x 45°/div = 76.5°
The above setup allows 45° per division but if more accu-
racy is required the SWEEP TIME/DIV may be changed and
magnified without touching the A VAR control and if
necessary the trigger level can be readjusted.
For this type of operation, the relationship of one division to
45° no longer holds. Phase difference is defined by the
formula as follow.
RELATIVE MEASUREMENTS
If the frequency and amplitude of some reference signal are
known,
an unknown signal may be measured for level and
frequency without use of the VOLTS/DIV or SWEEP
TIME/DIV for calibration.
The measurement is made in units relative to the reference
signal.
* Vertical Sensitivity
Setting the relative vertical sensitivity using a reference
sig-
nal.
1.
Apply the reference signal to the INPUT and adjust the
display for a normal waveform display.
5-6
Phase difference
Reference signal
1
cycle
Comparison
signal
Phase difference
Phase difference-
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