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D I F F E R E N C E
TIME
D E L A Y E D S W E E P
Synchronized waveforms which are skewed In time can be
accurately measured using the delayed sweep.
1. Apply the two signals to the channel 1 and channel 2 IN-
PUT jacks setting the vertical MODE to either A L T or
CHOP mode.
2. Set the SOURCE to the signal that is leading in phase
and adjust VOLTS/DIV and SWEEP TIME/DIV controls
for easy waveform observation.
Set the A VARIABLE control to C A L position.
3. Set the B MODE to initiate the S T A R T S AFTER DELAY
mode of operation. Set the HORIZ DISPLAY to A. Select
the HORIZ DISPLAY to A L T and use the • T R A C E SEP
control to adjust the B sweep for easy observation and
adjust the B SWEEP TIME/DIV and DELAY TIME MULT
controls to make the intensified portion coincide with
the rising edge or falling edge of the waveform that is to
be used as the reference.
4 . Using the DELAY TIME MULT adjust the pulse to any
convenient vertical graduation line and record the dial
reading at that point.
5. Using the DELAY TIME MULT adjust the corresponding
point on the second signal to the same vertical line and
record the reading of the dial at this point as well. The
time difference or skew of the two waveforms is then
the second dial reading minus the first dial reading
multiplied by the A SWEEP TIME/DIV control setting.
Using the formula:
Time difference = (2nd dial reading — 1st dial reading)
x Delayed sweep time (A SWEEP TIME/
DIV setting).
Fig. 34
[EXAMPLE]
The reference signal dial reading is 1.00 while the second
dial reading is 5.34 with an A SWEEP TIME/DIV setting of
2
us.
(See Fig. 34)
Substituting the value:
Time difference = ( 5 . 3 4 - 1 . 0 0 ) x 2 (/is) = 8.68 ps
28
M E A S U R E M E N T S
U S I N G
Read the dial setting when
B sweep points of D E L A Y
TIME MULT © and © are
in the same position.
X - Y A P P L I C A T I O N S
* Phase Shift Measurement
A method of phase measurement requires calculations bas-
ed on the Lissajous patterns obtained using X-Y operations.
Distortion due to non-linear amplification also can be
displayed.
A sine wave input is applied to the audio circuit being
tested. The same sine wave input is applied to the vertical
input of the oscilloscope, and the output of the tested cir-
cuit is applied to the horizontal input of the oscilloscope.
The amount of phase difference between the two signals
can be calculated from the resulting waveform.
To
make phase measurements, use the following pro-
cedure.
1. Using an audio signal generator with a pure sinusoidal
signal, apply a sine wave test signal at the desired test
frequency to the audio network being tested.
2. Set the signal generator output for the normal operating
level of the circuit being tested. If desired, the circuit's
output may be observed on the oscilloscope. If the test
circuit is overdriven, the sine wave display on the
oscilloscope is clipped and the signal level must be
reduced.
3. Connect the channel 2 probe to the output of the test
circuit.
4 . Select X - Y operation by placing the HORIZ DISPLAY
switch in the X - Y position.
5. Connect the channel 1 probe to the input of the test cir-
cuit.
(The input and output test connections to the vertical
and horizontal oscilloscope inputs may be reserved.)
6. Adjust the channel 1 and 2 gain controls for a suitable
viewing size.
7. Some typical results are shown in Fig. 3 6 .
If the two signals are in phase, the oscilloscope trace is a
straight diagonal line. If the vertical and horizontal gain
are properly adjusted, this line is at a 4 5 ° angle. A 9 0 °
phase shift produces a circular oscilloscope pattern.
Phase shift of less (or more) than 9 0 ° produces an ellip-
tical oscilloscope pattern. The amount of phase shift
can be calculated from the oscilloscope trace as shown
in Fig. 3 5 .
Fig. 35
SINE 0 =
—
A
Where <l>= phase angle
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