Bandwidth; Gai N; Off S E T - Tektronix 7a11 Instruction Manual

Operating Instructions-7A11
4. Repeat this
p
rocedu re
u
ntil no trace shift accompa-
nies switch ing betwee n + UP and
I
NVER T.
5. Chec k ST EP ΑΤΤΕΝ
B
AL adj ustment
b
y rotating the
V
OLTS/DIV switch thro ugh all
p
ositions and noting that
no trace sh ift occurs .
6. The ST EP ΑΤΤΕΝ BA L ad justment should be
r
e-
chec ked each time the 7Α 11 is used . Do
n
ot use the STEP
ΑΤΤΕΝ
B
AL
a
dj ustment as α position co ntrol .
ID EN TI FY
1 . De press the 7 A 1 1 ID EN TI F Y button wh ile observing
the trace.
N
ote that the trace shifts
u
pward app roximately
1/4
d
ivision when
t
he button is pu she
d
, and returns to its
previous position whe n t he bu tto n is
r
eleased.
2. If the oscilloscope is equip
p
e
d
with readout circu itry,
note that the word "IDEN TI FY" a
p
pears in the 7 A 1 1 read-
out area of the CRT while the ID EN TI FY
b
utton is
p
ushed .
The
d
eflection factor in use shoul
d
appear in the readout
area when the ID EN TI FY
b
utto n is released .
B
ANDWIDTH
1 . Ad just the oscillosco
p
e Inte nsity an
d
F
ocus controls
to obtain optimum trace sharpness.
2. Depress the FULL Band width switch and note that
the trace
b
ecomes slightly less clearly
d
efined. This occur s
b
ecause α much wi der frequency range is now
b
ei ng dis-
played, and the total noise increases accordingly.
Α
b
etter indication of bandwidth operatio n can
b
e ob-
tained by connecting the out
p
ut from α
h
ig h-fre quency gen-
erator to the STO RE D PROBE
I
NPUT.
W
it h 20 MHz
applied from the signal generator, and FULL selecte
d
at
7A1 1,
a
djust for 5 divisions of vertical
d
isplay . Then select
20 MHz at the 7 A 1 1 and note th at the vertical amplitude
d
ecreases to app roximately 3.5
d
ivisio ns .
GAI N
1 . Co nn ect α 50 Ω coaxial ca ble betwee n th e STO RE D
PR OBE
I
NPUT and the Cali brator o u tp ut
j
ac k at th e
oscilloscope .
2.
N
ote that with 0.4 V an
d
1 kH z selecte
d
at th e Cali-
brato r
a
nd .1
V
OL TS/DIV selected at the 7A1 1, α
d
isplay
of a
p
proximately 4
d
ivisions ap pears on the CRT .
2-6
A
djusting the GAI N control with the oscilloscope Cali-
br ator signal ap
p
lied provi des absolute accuracy to with in
2% i n
t
he ad justed position at temperatures
b
etween 0°C
an
d
50 °C. Other deflection factors will then be accu rate to
with in 4°/ ο absolute betwee n 0° C an d 50 ° C.
If greater gain accu racy is
r
equ ire
d
, α more accurate
amplit u de cali brator must be used and all instru me nts must
b
e
r
estricted to α temperatu re range of 15 °C to 35°C. The
Te ktronix Amplitude Calibrator and Comparator,
P
art No .
067-0502-01 is
r
ecommended for this pu rpose. An absolute
accur acy approaching 2% may then be obtained over the
ra n ge of
d
eflection factors.
P
O LAR ITY
1 . Disconnect the coaxial cable from t
h
e STO RE D
PR O BE
I
NPUT Adapter. Then
a
d
just the 7Α11 POSI-
TION co ntrol as
n
ecessary to
p
lace the trace at gratic ule
vertical ce n te r.
2. Re-connect the coaxial cable to the STORE D PR OBE
I
NPUT Adapter and note that the 1 kH z square wave is
displayed in α
p
ositive or
u
p
war
d
d
irection from the refer-
ence position established at graticule center.
3 . At the 7A1 1, depress the INVER T button .
N
ote that
now the
p
ositive-going square wave is deflected in α down-
wa rd d irection on the CRT.
4 . De press the +UP butto n to
r
egain upward deflection
of the
p
ositive-going squ are wave .
O
FF SET
1 . Adjust the outer OFF SET kn ob as necessary to place
its white marker at 0.
2. Depress the O FF S E T ON b
utton. The trace may shift
upwar
d
or downward .
3.
M ove the O FF S E T controls and note trace reaction .
Cloc kwise moveme nt ca u ses up ward deflectio n, while
co un tercloc kwise movement ca uses
d
ow nward deflection .
Also
n
ote that th e
F
I NE co ntrol knob ca uses co nsi d e rably
less reaction tha n
t
he COA R S E co ntr ol kn ob. (T he two
knobs
h
ave α
r
atio of app roximately 10 :1 .)
4. Depress the OFF SET OFF bu tton . The squ are wave
d
isplay shou ld now app ear in the upp er
h alf of the CRT.
Ο