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13. APPLICATION OF X-Y OPERATION
* Phase Measurement
The X - Y operation can be used for phase measurement.
Typical application covers measurement of phase distortion
in circuits designed to produce a certain phase shift and au-
dio amplifiers.
Distortion amplitude can be measured at the same time.
Phase measurement is made as follows:
1)
Apply sine w a v e w i t h little distortion to the audio cir-
cuit to be tested.
2)
Set the signal generator output to the normal operation
level of the circuit to be tested. Observe output of the
circuit on the C R T . If e x c e s s i v e signal is input to the
circuit, the displayed w a v e f o r m is clipped; reduce the
signal level in s u c h a c a s e .
3)
Connect the C H 1 probe to the output of the circuit to
be tested.
4)
Select X - Y of the H O R I Z O N T A L MODE s w i t c h e s .
5)
Connect the C H 2 probe to the input of the circuit to
be tested.
6)
Adjust channel-1 and channel-2 gains to obtain the Lis-
sajous' pattern of a proper size.
7)
Fig. 0 0 s h o w s typical examples. If the t w o signals are
equal in phase, the Lissajous' pattern is a straight di-
agonal line. It is at 4 5 ° if the vertical and horizontal
gains are set to the s a m e level. A 9 0 ° phase shift
produces a circular Lissajous' pattern. Phase shift more
or less than 9 0 ° produces an elliptical Lissajous' pat-
tern. T h e amount of actual phase shift is calculated as
follows:
Calculation of phase difference:
R
Sin <j> =
Where 0 = phase angle
A
Fig. 4 9
36
N o
a m p l i t u d e
N o p h a s e
d i s t o r t i o n
d i f f e r e n c e
W i t h
a m p l i t u d e
N o p h a s e
d i s t o r t i o n
d i f f e r e n c e
W i t h
1 8 0 °
N o
a m p l i t u d e
p h a s e
d i s t o r t i o n
d i f f e r e n c e
Fig. 50 Typical Display of Phase Measurement
* Frequency Measurement
In addition to the phase measurement, frequency can be
measured from the Lissajous' pattern.
1)
Apply sine w a v e of known frequency to the C H 2 input
connector
of the oscilloscope. Select X - Y of the
H O R I Z O N T A L MODE s w i t c h e s .
2)
Connect the C H 1 probe to the unknown signal.
3)
Adjust the channel-1 and channel-2 gains.
4)
The resulting Lissajous' pattern s h o w s the ratio be-
t w e e n the t w o frequencies.
U n k n o w n f r e q u e n c y t o v e r t i c a l i n p u t
R a t i o of
u n k n o w n
R e f e r e n c e f r e q u e n c y t o h o r i z o n t a l
t o
r e f e r e n c e
Fig. 51 Lissajous' Pattern used for Frequency
Measurement
N o
a m p l i t u d e
W i t h p h a s e
d i s t o r t i o n
d i s t o r t i o n
W i t h
a m p l i t u d e
W i t h p h a s e
d i s t o r t i o n
d i f f e r e n c e
W i t h
9 0 °
N o
a m p l i t u d e
p h a s e
d i s t o r t i o n
d i f f e r e n c e
i n p u t
I
:
I
'4
:
I
6
:
1
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