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9. PHASE DIFFERENCE MEASUREMENT
| 1 )
Normal Procedures
T h e following describes the normal procedures for measur-
ing phase difference of t w o signals (sine w a v e , for e x a m -
ple) of the same frequency.
1)
Apply t w o signals to the C H 1 and C H 2 input connec-
tors. Select A L T or C H O P of the V E R T I C A L MODE
s w i t c h e s .
2)
Set each control for normal s w e e p display. Set the
S O U R C E s w i t c h to the signal w h i c h is leading in phase
(reference signal), and adjust the signals so that they
have the same amplitude with the V O L T S / D I V and
V A R I A B L E controls.
3)
Adjust one cycle width of each waveform to 8 divisions
with the S W E E P T I M E / D I V and V A R I A B L E controls.
Set the t w o signals to the center of the C R T with the
t POSITION controls. Through the above adjustment,
one division now represents 4 5 ° ( 3 6 0 ° / 8 div). T h u s ,
the s w e e p coefficient is given as 4 5 ° / d i v .
4)
Measure the horizontal distance between the cor-
responding points on the t w o w a v e f o r m s , and multi-
ply the distance by the s w e e p coefficient ( 4 5 ° / d i v ) .
Phase difference (deg) =
Horizontal distance (div) x 4 5 ° / d i v
O n e c y c l e (8 d i v )
R e f e r e n c e s i g n a l
C o m p a r i s o n s i g n a l
Fig.
[ E X A M P L E ]
In the example s h o w n in Fig. 4 1 , the measured horizon-
tal distance is 1.7 divisions, w h i c h gives
Phase distance = 1.7 (div) x 4 5 ° / d i v = 7 6 . 5 °
T h e above setup allows 4 5 ° per division, but if more a c -
curacy is required, setting of the S W E E P T I M E / D I V may be
changed to magnify the w a v e f o r m without touching the
V A R I A B L E control. If n e c e s s a r y , the T R I G G E R I N G L E V E L
control can be readjusted.
In this method, the phase difference can be determined a s
s h o w n below from the relationship between the S W E E P
T I M E / D I V setting for 8 div/cycle and new S W E E P T I M E / D I V
setting made for better a c c u r a c y .
36
P h a s e
d i f f e r e n c e
4 1
Phase difference
= Horizontal distance of n e w s w e e p range (div)
x 4 5 ° / d i v
n e w S W E E P T I M E / D I V setting
x
original S W E E P T I M E / D I V setting
For easy operation, use " x 10 M A G " , w h i c h provides the
s w e e p coefficient of 4 . 5 ° .
P h a s e d i f f e r e n c e
In c a s e o n e c y c l e =
A t m a g n i f i e d s w e e p c o e f f i c i e n t
Fig. 4 2
(1) Cursor Measurement Procedures
1)
Bring the w a v e f o r m to be measured to an easy-to-see
position according to items 1) and 2) of the normal
procedures.
2)
Adjust the one c y c l e width of each w a v e f o r m to 5 di-
visions with the S W E E P T I M E / D I V and V A R I A B L E con-
trols. Bring the t w o signals to the center of the C R T with
the T POSITION controls.
3)
Select the MAT cursor mode w i t h the C U R S O R S .
NOTE: Phase difference can be measured w h e n the
S W E E P T I M E is not set to C A L .
4)
Adjust the AHEF cursor to the point w h e r e the signal
with the leading phase crosses the center horizontal
graduation line, and adjust the ^ c u r s o r to the point
w h e r e the signal with the delayed phase c r o s s e s the
center horizontal graduation line.
5)
Measured phase difference is displayed following
P H A S E in the upper right of the C R T .
8 d i v .
P h a s e d i f f e r e n c e
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