Tektronix 454A - Page 53

Ti me- Di f f er ence M easur ement s
T h e cal i br at e d swee p r at e an d d ual - t r ace f eat ur es of t h e
454zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ‘ al l ow measur eme nt of t i me d i f f er ence bet wee n t wo
se p ar at e event s . To measur e t i me di f f er ence,
use t h e
f ol l owi n g p r oce d ur e :
1
.
Set t
h e I n p ut Cou p l i n g swi t ch es t o t h e d esi r e d
cou p
l i ng posi t i ons .
2 . Set t h e M OD E swi t c h t o ei t h er CHO P or A L T . I n
gener al , CH O P i s mor e s u i t abl e f or l ow- f r equency si gnal s
an d t h e A L T p osi t i on i s mor e sui t abl e
f or h
i g h - f r e q uency
si gnal s
.
M or e i nf or mat i on
on
det er mi n i n g t he mo d e i s gi ven
un d er Dual - Tr ace O p er at i on i n t h i s sect i on .
3 . Set t h e T R I GG ER swi t c h t o CH 1 O NL Y .
6 .
Set t he V
O
L TS/ DI V swi t c h
es
t o pr o d
uce
f our -
or
f i ve- di vi si on d i s p l ays .

U si ng t h e f or mul a :
7 . Set t he ‘ LEVEL con t r ol f or ± st abl e di s p l ay .
8 . I f p ossi bl e, set t he ¤™œ• / DI V swi t c h f or ± sweep r at e
w h i c h s h ows t h r ee or mor e di vi si o n s bet ween t he t wo
wavef or ms .
9 . Ad j ust t he ver t i cal P OSI TI O N cont r ol s t o cent er eac h
wavef or m ( or t h e poi nt s on t he d i s p l ay bet ween w h i c h t he
measur eme
nt i s ma d e) i n r el at i on t o t h e cent er h or i zont al
l i ne .
10 . A d j ust t he h or i zont al P OSI TI ON cont r ol so t h e
C h annel 1 ( r ef er ence) wavef or m cr osses t he cent er
h or i zont al l i ne at ± ver t i cal gr at i cul e l i n e .
O p er at i ng I nst r uct i ons- 454 ‘ / R 454A
C
h annel 1 ( r ef er e n ce)

C h a nn el 2
i . i WEEMEWEE1
ENEENI MI NE
4 . Connect t he r ef er ence si gnal t o I NPU T C H 1 an d t h e
com p ar i son si gnal t o I NPU T CH 2 . T he r ef er ence si g n al

F i g . 2- 23 . M easur i n g t i me d i f f er e n ce bet ween t wo pul ses .
s houl d pr ecede t h e com p ar i son si gnal i n t i me . U se coaxi al
cabl es or p r obes w h i c h have equal t i me d el ay t o connect
t h e si gnal s t o t he I NPU T co n nect or s .

12 . M ul t i p l y t he measur e d d i f f er ence by t he set t i ng of
t h e ¤™œ• / DI V swi t c h . I f swee p magni f i cat i o n i s used,
d i vi d e t h i s answer by 10 .
5 . I f t he si gnal s ar e of o pp osi t e pol ar i t y,
pul l out t h
e
I NVER T swi t c h t o i n ver t t he C hannel 2 d i s p l ay ( si gnal s
may be of o pp osi t e p ol ar i t y due t o 180 ° ph ase di f f er ence ;

E xampl e . Assume t h at t h e ¤™œ• / DI V swi t c h i s set t o
i f so, t a k e t h i s i nt o account i n t he f i n al cal cul at i on) .

50 ¼ s,

t he

M AG

swi t c h  t o

§ 10

an d

t h e

h or i zont al
d i f f er ence bet ween wavef or ms i s 4 . 5 d i vi si ons ( see F i g .
2- 23) .
¤™œ• / DI V
hor i zont al
§
di f f er ence
Ti me Del ay
=

set t i ng

( d
i vi si ons)
magni f i cat i on
Subst i t ut i ng t h e gi ven val ues :
Ti me Del ay =
50 ¼ s §
4
. 5
10
T h e t i me d el ay i s 22 . 5 mi cr osecon d s .
Del aye d or M i xe d Swee p Ti me M easur ement
T he d el ayed sweep mo de can be use d t o ma ke acc u r at e
t i me measur ement s . T he f ol l owi ng meas u r eme n t d et er mi nes
t h
e
t i me d i f f er ence b et ween t wo p ul ses di s p l aye d on t he
same t r ace . T h i s a p pl i cat i on may
al so be used t o measur e
t i me di f f er ence f r om t wo d i f f er ent sour ces ( d ual - t r ace) or
t o measur e t i me d ur at i on of ± si ngl e p ul se .
11 . M easur e t h e h or i zont al d i f f er ence b et ween t he
C hannel 1 wavef or m an d t he C h annel 2 wavef or m ( see F i g .

1 . Co nnect t h e si g n al t o ei t h er I NPU T connect or . Set
2- 23) .

t h e M OD E swi t c h t o di s p l ay t h e c h annel use d .
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