Tektronix 454A - Page 49

7 . Set
t
h
e
I n p
ut Cou p l i ng swi t c h t o DC . T h e gr ound

U si ng t h e f or m u l a :
r ef er ence l i ne ca n be c h ec k e d at
any
t i me by swi t c h i ng t o
t h e G N D p osi t i o n .
I nst ant aneous _
V ol t age
8 . Set t h ezyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA ‘ Tr i gger i n g cont r ol s t o obt ai n ± st a b l e

ver t i cal

VO L
TS/ DI V

p
r obe
di s p l ay . Set t h e ¤™œ• / DI V swi t c h t o ± set t i n g t h at d i s p l ays

d i st ance

§

p ol ar i t y

§

set t i ng

§
at t e n uat i on
sever al cycl es of t h e si gnal .

( d i vi si ons

f act or
F i g .
2- 20 . M eas ur i n g i n st a n t a n eo u s DC vol t age wi t h r
es p ect t o ±
r ef er e n ce vol t age .
Ÿ
Subst i t ut i ng t he gi ven
val ues :
9 . M eas u r e t h e d i st a n ce i n d i vi si ons bet ween t he
r ef er e n ce l i ne an d t h e p oi nt on t h e wavef or m at w h i c h t he

I nst ant aneous

=
4 . 6X+1 § 2
V § 10
DC l evel i s t o b e measur e d . F or exam p l e, i n F i g . 2- 20 t
h
e

V ol t age
measur ement i s ma d e bet ween t h e r ef er ence l i ne and poi nt
‘ .

T h e i nst a n t aneo u s vol t age
i s +92 vol t s .
O p er at i ng I nst r uct i ons- 454 ‘ / R 454A
10 . E st abl i s h t h e p ol ar i t y of t h e si g n al . I f t h e wavef or m

Com p ar
i
son M easur ement s
i s above t h e r ef er e n
ce
l i n e, t h e vol t age
i s p osi t i ve
;
bel ow t h e

I n some a p pl i cat i ons i t may b e d esi r abl e t o est abl i s h
l i ne, negat i ve
( w
h en t h e I
NVER T
swi t c h
i s
p
us h
e
d i n i f
usi ng C h annel 2) .

ar b i t r ar y un i t s of measur ement ot h er t h a n t h ose i ndi cat ed
by t h e VO L TS/ DI V swi t c h or ¤™œ• / DI
V swi t c h . T h i s i s
p ar t i cul ar l y usef u l w
h
en
compar i ng u n known si gnal s t o ±
r ef er ence ampl i t u
d e or r e p et i t i o n r at e . One use f or t h e
11 . M ul t i p
l y
t
he di st a n
ce meas u
r e d i n st e p
9
by
t h e

com p ar i son- measur eme n t t ec h ni q ue i s t o f aci l i t at e cal i br a-
V
O
L TS/ DI V swi t c h set t i ng . I ncl ude t h e at t enuat i on f act or

t i on of
e
q ui pme n t ( e . g . , on an assembl y- l i ne t est ) w h er e t h e
of t h e p r obe i f any .

d esi r e d am p l i t u d e or r e p et i t i on r at e does n ot p r o d uce an
exact number of d i vi si ons of def l ect i on . T h e ad j ust me n t
wi l l be easi er an d mor e accur at e i f ar bi t r ar y uni t s of
measur ement ar e est a
b l i s he d so t h at cor r ect ad j ust ment i s
i n d i cat e d by
an exact num b er of
d
i vi si on of d ef l ect i on .
E xampl e . Ass u me t hat t he ver t i cal di st ance meas u r e d i s

Ar b
i t r ar y swee p r at es can be usef ul f or com p ar i n g h ar mo n i c
4 . 6 d i vi si o n s ( see F i g . 2- 20) , t h e wavef or m i s a b ove t h e

si g n al s t o ± f undament al f r e q uency, or f or comp ar i ng t h e
r ef er ence l i n e, u si ng ± 10 § at t e nu at or pr obe and ±

r e p et i t i on r at e of t h e i nput an d out put p ul ses i n ± di gi t al
VO L TS/ DI V swi t c h set t i ng of 2 .

count - d own ci r cui t . T
h e f ol l owi n g pr ocedur e d escr i bes h ow
t o
est abl i s h ar
b
i t r ar y u n i t s of meas u r e f or compar i son
measur ement s . Al t h oug h t h e pr oce du r e f or est abl i s h i ng
ver t i cal an d h or i zont al ar b i t r ar y uni t s of measur ement i s
m u c h t h e same, bot h p r ocesses ar e descr i bed i n d et ai l .
V er t i cal Def l ect i o n
F act or . To est abl i s h an ar bi t r ar y
ver t i cal d ef l ect i on f act or base d upon ± speci f i c r ef er ence
ampl i t u d e, p r ocee d as f ol l ows :
1 .
Connect t h e r ef er ence si gnal t o t h e I NPU T
connect or . Set t h e ¤™œ• / DI V swi t c h
t o d i s p l ay sever al
Ver t i cal

cycl es of t he si gnal .
d i st a n ce
2 . Set t h e V O L TS/ DI V swi t c h an d t he V A R I A BLE
- - -

VO L TS/ DI V co n t r ol t o p r oduce ± di s p l ay an exact num b er
R ef er e n ce l i n e

of gr at i cul e di vi si o n s i n ampl i t u d e .

Do not c
h
ange t h e
VA R I A BLE V O L TS/ DI V cont r ol af t er o b t ai ni ng t h e
desi r e d d ef l ect i on . T h i s di s p l ay can be use d as ± r ef er ence
f or am p l i t u d e compar i son meas u r ement s .
2- 3 1