Tektronix 434, Инструкция по эксплуатации

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O p erating In s tru c tio n s —4 3 4
10. A d ju s t th e h o riz o n ta l P O S IT IO N c o n tro l so the
Channel 1 (reference) w a ve fo rm crosses the center h o r i­
zo n ta l line at a v e rtic a l g ra tic u le line.
4 3 4 . T h is m e th o d o f phase d iffe re n c e m easurem ent can be
used up to the fre q u e n c y lim it o f th e ve rtic a l system . T o
make th e c o m p a riso n , use th e fo llo w in g procedure.
1 1 . M easure th e h o riz o n ta l distance betw een the
Channel 1 w a v e fo rm and th e Channel 2 w a ve fo rm (see Fig.
2
-
11
).
12. M u ltip ly the measured distance b y th e se ttin g o f the
T IM E /D IV s w itc h .
E X A M P L E , Assume th a t th e T IM E /D IV sw itch is set to
50 /us and th e h o riz o n ta l distance between w a ve fo rm s is 4.5
divisio n s (see Fig. 2-11).
1. Set th e In p u t C o u p lin g sw itches to the same p o s itio n ,
depending on th e ty p e o f c o u p lin g desired.
2. Set th e V e rtic a l M ode sw itch to e ith e r CHOP or A L T .
In general, CHOP is m ore suitable fo r lo w -fre q u e n c y signals
and the A L T p o s itio n is m ore suitable fo r h ig h -fre q u e n c y
signals. M ore in fo rm a tio n on d e te rm in in g th e m ode is given
u n d e r D ual-Trace O p e ra tio n in th is section.
3. Set th e T R IG G E R S O U RC E sw itch to CH 1.
Using the fo rm u la :
T im e D elay
T IM E /D IV
se ttin g
h o riz o n ta l
distance
(divisions)
S u b s titu tin g the given values:
4. C o n n ect the reference signal to th e CH 1 c o n n e c to r
and th e com parison signal to th e CH 2 c o n n e c to r. T he
reference signal should precede th e com parison signal in
tim e . Use coaxial cables o r probes w h ic h have sim ila r tim e
de la y characteristics to co n n e c t th e signals to th e in p u t
co nnectors.
T im e D elay = 50 /is X 4.5
The tim e delay is 2 2 5 m icroseconds.
M u lti-T ra ce Phase D iffe re nce Measurements
Phase co m p a riso n betw een tw o signals o f th e same
fre q u e n c y can be made using the dual-trace fe a tu re o f the
5. If the signals are o f o p p o site p o la rity , set th e
IN V E R T s w itch o u t to in v e rt th e Channel 2 d isp la y.
(Signals m ay be o f opposite p o la rity due to 180° phase
d iffe re n c e ; i f so, take th is in to a c c o u n t in th e fin a l calcula­
tio n .)
6. Set th e V O L T S /D IV sw itches and the V aria b le
V O L T S /D IV c o n tro ls so th e displays are equal and a b o u t
fiv e d ivisio n s in a m p litu d e .
C h a n n e l 1 (re fe re n c e ) C h a n n e l 2
\ 7
50 %
\
t
A m p l i t u d e _
level
\
A
H o r iz o n ta l —
d iffe re n c e
F ig . 2 -1 1 . M e a s u rin g tim e d iffe re n c e b e tw e e n t w o pulses.
7. Set th e T R IG G E R c o n tro ls to o b ta in a stable d isp la y.
8. Set th e T IM E /D IV sw itch to a sweep rate w h ich
displays a b o u t one cycle o f th e w a ve fo rm .
9. Move th e w a ve fo rm s to th e center o f th e g ra ticu le
w ith th e v e rtic a l P O S IT IO N c o n tro ls .
10. T u rn the V a ria b le T IM E /D IV c o n tro l u n til one
cycle o f th e reference signal (Channel 1) occupies e x a c tly
e ig h t d ivisio n s betw een th e second and te n th v e rtica l lines
o f th e g ra tic u le (see Fig. 2-12). Each d iv is io n o f the g ra ti­
cule represents 4 5 ° o f th e cycle (3 6 0 ° -5- 8 divisio n s =
4 " /d iv is io n ). The sweep rate can be stated in term s o f
degrees as 4 5 °/d iv is io n .
11. Measure th e h o riz o n ta l d iffe re n c e between corres­
p o n d in g p o in ts on th e w aveform s.
2-21