Tektronix 576 - Page 26

Op
erating Inst r uctions-Ty pe 576
Wh en ma k ing α
measurement using t he DIS PL AY O FF-
SET controls, t
he C
R
T graticule becomes α win d ow . Wh en
t he C
EN
T
ERL I NE VA LUE switch is set to 0, t he vertical
cente r
line
( h orizontal offset) or t he h orizontal centerline
(vertical offset) of t h
e
win d ow
is
at
t he ze r o signal portion
of t h
e
d is p lay . As
t he C EN T ERL I NE VA LUE switc h is
turne d countercloc k wise, t h e win d ow moves eit h er ver-
tically or h orizontally along t he d is p lay . F or each p osition
of t h e C EN T ERL I NE VA LUE switc h , t he number on t h e
switch app ea r ing in t he blue win d ow re p resents t he nu mber
of d ivisions t h e vertical centerline or t he h orizontal center-
line h as been offset from t he zero offset line . If t he d is p lay
h as been magnifie d , t h e number in t he blue win d ow must
be multi p lie d by 10 .
T he ZERO button p rovi des α convenient means of
p osi-
tioning t he zero reference point on t he C R T graticule . U n-
d er normal op erating con d itions (DIS PL AY O FF S
E
T Selec-
tor switch set to N O RM) w hen t h e
Z
ER O button is p ressed,
α
zero reference s p ot appears on t he C R T graticule . T h is
spot in d icates t he point on t h e CR T w h ere zero signal is
being measure d by t he vertical and
horizontal d is p lay
am p lifiers . Wit h t he b u tton p resse d , t
he p
ositioning
con-
trols may be used to p osition t h
e
s pot to α p oi n t
on
t h
e
C R T
graticule w
h ic h
ma
kes measurements co n venient . If
t he DIS PL AY O FF S
E
T Selector switc
h
is set to
VER T or
HOR IZ, t he zero reference p oint in d icates t h
e
h orizontal o
r
vertical graticule line, res p ectively, to w
h
ic h t h
e
C
EN T ER-
L I NE VA LUE switch setting a pp lies . To assure t
h e acc u -
racy of t
he
C EN T
ERL
I NE
V
A
LUE switc h settings, t he zero
reference s p
ot
s
hould be a d j
uste
d
(using
t
h e p
ositio
n
ing
controls) to t he app ropriate cen terline for t he offset being
use d . For maximum accuracy of measurement, t he p osition
of t h is zero reference p oint s hou l d be a d ju ste d wit h t h
e
DIS PL AY O FF S ET Selector switch in one of its M AG N I-
F I ER p ositions .
T h e CA L button p rovi des α means of chec k ing t
he cali-
bration
of t he d is p lay am p lifiers . U nd er normal o p erating
con d itions
(DIS PL AY O FF S E T Selector switc h set to
N O RM) w
hen t he CA L button is p ressed, α calibration ref-
erence s pot a pp ears on t h e CR T . T h is s pot re p resents α
signal ap p lie d to bot h t he vertical an d t h
e h
orizontal
dis-
p lay am p lifiers w h ic h s h oul d cause 10 d ivisions d
eflection
on t he CR T graticule bot h vertically an d
h orizontally . If
t he p osition of t h is s pot is com
p are d wit h t h e position of
t he spot obtaine d w
hen
t
he Z ER O button is presse d , t h e
accuracy
of calibration of t he dis p lay am p lifiers can be d e-
termine d . Wh en t h e DIS PL AY O FF S E T Selector switc h is
set to
eit h er VER T or HOR IZ, t he calibration reference
sp
ot
s h oul d ap pear on t he vertical cen terline ( h orizontal
offset) or t he h orizontal centerline (vertical offset), as-
suming t h e zero reference point is p ro p erly a d j uste d . T h is
calibration c hec k s hould be ma de wit h t h e DIS PL AY O FF-
S E T Selector switch in eit her H O R IZ X10 or VERT X10 .
Any d
e p arture
of
t he calibration reference s pot from t h e
centerline, w
h
en
t h
is
chec k is ma d e, re p resents an error of
1 ° / ο p
er d ivision in t h e d is p lay offset .
2- 1 8
T h e DIS PL AY I NVER T button provi des α means of
in-
verting t h e d is p lay on t he CRT . Wh en t h
e
DIS PL AY IN-
VERT button is p us he d , t he in puts to t h
e
d is p lay am
p
lifiers
a r e reverse d , causing t h e d is p lay on t he CRT to be inverte d
bot h vertically an d h orizontally abo u t t he center of t h
e
gratic u le .
If t he p osition controls are centered , t he ze r o an d
calibration r eferences s p ots s hould ap p ear in p articular
p ositions on t he graticule dep en d ing on t h e p ositions of
t he P O L A R ITY switc h an d t he DIS PL AYO FF S
E
T
Selector switch . F ig . 2-20 s h ows t hese positions of t
he
spot for t he various settings of t he two switc
h
es . To
d etermine t he s pot positions w h en t
he
I
NVER T button is
p resse d , ass u me t h
e
graticule s
h
own is
inverte d bot h
vertically and h orizontally .
V ertical M easurement and Deflection F actor
In t he vertical d imension, t he d is p lay on t h e C R T meas-
ures eit h er collector current (IC), emitter current ( ΙΕ ) or
t h
e
out p ut of
t h e Ste p Generator . T he M OD E switch an d
t h e VER TICA L
switc
h d etermine w
h
ic
h
of
t h ese measure-
ments are ma d e .
T he V ertical d eflection factor of t h
e
d is p lay on
t he C RT
is controlle d by t he VER TICA L switch , t
he
DIS
PL AY
O
FF S E T Selector switch and t he M OD E switch . T he PER
VER T DI V rea d out to
t he rig h t of t he CRT in d icates t h e
vertical d eflection
factor
d
ue
to t
he combine
d
effects of
t h ese t h ree cont r ols .
U nd er normal op erating con d itions, wit h t he M OD E
switch set to N O RM and t he DIS PL AY O FF S ET Selector
switch set to N O RM (O FF), collector current is measure d
vertically and
t he VER TICA L switc h dete r mines t h e verti-
cal sensitivity of t h e dis p lay .
Wh en meas u ring collector current, t h e VER TICA L
switch p rovi d
es d eflection factors (unmagnifie d ) ranging
from 1 μΑ / d ivision to 2 Α / d ivision . T h e vertical d eflection
factor is in d icate d eit
h
er by t
he PER VER T DI V
rea
d out or
by t he p osition of t h e VER TICA L switch , using t h
e letters
p rinte d in blac k to d etermine units . T h e rea d out a n d t he
switch p osition s hould coinci de .
Wh en t he M OD E switch is
set
to LE A K AG
E (EMITTER
C URREN T) t he CR T d is p lay
measures emitter current ver-
tically . In t h is case t
he vertical sensitivity of t h e d is p lay is
increase d by 1000 times for
each p osition of t h e VER-
TICA L switc
h . T he vertical deflection factor is in d icate d
eit her by t he PER VER T DI V rea d out or by t h e p osition of
t he VER
TICA
L switch , using t h e letters printe d in orange
to d etermine units . Wh en t he M OD E switch is set to LE A K-
AG E t h e out put of t he Collector Su pply is DC voltage, li k
e
t h at obtaine d w hen t he M OD E switch is set to DC (ANTI
L OO P ), rat h er t h an α voltage swee p . Also in t h
e lea k
age
mo d e α slig h t error (up to 1 .25 V) is add
e
d to t h
e horizon-
tal d is p lay . T h e following H orizontal
M easurementan d De-
flection F actor sectio
n s h ows h ow to d etermine t he d egree
of t
h is error .