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2. The S w e e p (horizontal) calibration coefficient is then
the period of the reference signal divided by the product
of the number of divisions used in step 1 for setup of the
reference and the setting of the S W E E P TIME/DIV con-
trol.
Using the formula:
Sweep coefficient
Period of the reference signal (sec)
horizontal width (div) x S W E E P TIME/DIV setting
3 . Remove the reference signal and input the unknown
signal, adjusting the S W E E P TIME/DIV control for easy
observation.
Measure the width of one cycle in divisions and use the
following relationship to calculate the actual period.
Using the formula:
Period of unknown signal = Width of 1 cycle (div) x sweep
coefficient x S W E E P TIME/DIV setting
Adjusted reference signal
Reference signal
Unknown signal
Fig. 37
28
[ E X A M P L E ]
S W E E P
TIME/DIV
is 0.1 ms/div
reference signal. Adjust the V A R I A B L E so that the distance
of one cycle is 5 divisions.
Substituting the given value:
,
Horizontal coefficient =
5 (div) x 0.1 (ms/div)
= 1.143
Then,
S W E E P
T I M E / D I V is 0 . 2 ms/div
amplitude is 7 divisions. (See Fig. 3 7 )
Substituting the given value:
Pulse width = 7 ( d i v ) x 1 . 1 4 3 x 0 . 2 (ms/div) = 1.6 ms
1 3 .
APPLICATION OF X-Y OPERATION
•
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
displayed.
A sine w a v e input is applied to the audio circuit being
tested. T h e same sine w a v e 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 t w o 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 w a v e 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 w a v e 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 T R I G MODE 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 9 .
If the t w o 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. T h e amount of phase shift
can be calculated from the oscilloscope trace as s h o w n
in Fig. 3 8 .
and
apply
1.75 kHz
1.75 (kHz)"
1
and
horizontal
amplification
also can be
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