Tektronix SC 502, Инструкция по эксплуатации

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Operating Instructlons-SC
502
triggering from c o m p le x waveforms, thi s position i s useful
for provid i ng a stable d i s p l a y of the high-frequency
com ponents.
Trigger Slope
The trigger SLOPE switch determi nes whether the
t
r i
g
g
er
circuit re
s
po
n
d s on the positive-goi ng or negative­
goi ng portion of the
t
ri
g
ger signal. When
the SLO PE
switch is in the + (positive-goi ng) position, the display
starts with the positive-going p o rt io n of the waveform; in
the
- (negative-goi ng) position, the display starts with the
negative-goi ng portion of the w a
v
e
f
o r m . When several
cycles
of a
s
i g n al appear in
t
h e display, the setti ng of t h
e
SLOPE switch is often unimportant. H o w e
v
e
r
,
if only a
certain portion
o f a c
y c l
e
is
to be
displayed, correct setti ng
of the SLOPE switch is important
to
provide a d i s p la y that
starts on the desired s lo p e of the
input
signal.
Trigger Level
The trigger LEVEL control determines t h e voltage
level
on the
triggeri ng
waveform at which th e
sweep
is
triggered.
When the LEVEL control is set
in
the
+
re
g
i
o
n
,
the tri
gger ci
rcuit responds at a more positive poi nt on the
trigger signal. When the LEVEL control is set
In
the
-
region, the t r i gg e
r
circuit responds at a more negative
poi nt on the t
r
i gg e r Sig nal. To s e t the LEVEL control , first
select the tr i g g e
r
SOURCE, COUPLI NG,
and SLO PE.
Then set the
LEVEL
control fully
cl ockwise
and rotate
it
counterclockwise
until
the
display
starts
at
the desired
point.
Trigger Mode
Automatic Triggering. The AUTO
position (AUTO
button pushed i n ) of the trigger mode switch provi des a
stable display when the LEVEL
c
o n tr o
l
is
correctly
set (see
Trigger Level portion of General O p e ra
t
i n g I nform ati on)
and
an
adequate t
r
i
g g e
r
s i gn
a
l is present. The TR I G ' O
light i ndicates when the sweep generator
is
triggered.
When
the trigger repetiti on rate is less
than
about
20 Hz,
or
in the absence of an adequate tri gger s
i
g n
a
l
,
the
sweep generator
f
r e e- r u n s to prod uce a reference trace.
When an adequate trigger S i g na l is agai n a ppl i e d , the free
runni ng condition ends and the
sweep
generator is
triggered to
pr
o d u c e a stable d
i
s
p
l a
y
(with the c o r r
e
ct
LEVEL c
o
n t r o
l
setting).
Normal
Triggering.
Operation
in
the norm al position
( AUTO button is out) of the trigger mode switch is the
same
as
i n t
h e
AUTO position when
a
trigger
Signal is
applied. However, w
h
e n
a
t r i g
g
e r si gnal is not present, the
sweep generator remains off and there is no d i spl a y
.
The
TRI G ' O li g
h
t indicates when
the
sweep
generator
is
t
r
i
g g e r e d.
2-8
Use the normal mode to display Signals with repetition
rates be/ow about 20
Hz.
This m o d e provides an i ndication
of
an
adequate trigger Signal as well as the corrections of
trigger control settings, since there is no d i s
pl
a
y
wit hout
proper trigger. Also, the TRI G ' O l i g h t is off
when
t
h
e
sweep is not c or r
ect
l y triggered.
Trigger Hoidoff. By
placing the i nternal HO-SWP
j u m per i n the HO position, the variable sweep control
(CAL) is c o n ne c
t
ed as a Trigger Holdoff vari able
control.
In
this
configuration,
the
control
provides
for stable
triggeri ng
on aperiodic or
irregul ar
s
i
g
n
al
s
(such
as
complex
digital words). (The i n
t e
rn a l j um per
shoul d
only
be
changed by qualified personnel.)
To use
the
control, first obtai n the m ost stabl e presen­
tation possi ble by adjusti ng the triggeri ng controls in
the
normal manner.
Now,
rotate the Tri gger Holdoff
vari able
control counterclockwise until any remai ning
i nstability
is
eliminated.
Single Sweep. When the signal to be d i
sp
l a
y
ed is not
repetitive or varies in amplitude,
shape,
or time, a conven­
tional d
i
s p
l
a
y
may produce an u n
st
a b
l
e
presentation.
To
avoid this, use the Single-sweep feature.
The
sl ngle-sweep
mode
can
also
be
u
s
ed to p
h
o
t
o
g
r aph
a non-repetitive
s i g n a l .
To use the single-sweep mode,
first
make sure the
T
r i g
g
e
r ci rcuit
will respond to the event to
be di spl ayed.
Set the
AUTO
and SI NG LE SWP buttons to the out
position and o btai n the best possi ble display in
the
normal
manner (for random signals set the tri gger ci rcuit
to
trigger on a
s
i
g
n
a l
which is
approximatel y the same
am pl itude
and
frequency as
the random
signal).
Then.
depress the SI NGL SWP button and press and release the
RESET button. The next trigger p u l s e wi ll i nitiate the
s wee p and a s i n g l e trace will be presented on the screen.
After
this sweep is c o m p l e t e
,
the s w
ee
p generator is
"Iocked out" u nt i l reset. The
REAOY
i n d i c a t o
r
lights when
the sweep generator circuit has
been
reset and
is
ready
to
p r o du c e a
s
w ee p ; it goes out after the sweep is com plete.
To p r e p
a r
e the circuit for another single-sweep di spl ay,
press and release the
RESET button
agai n.
Horizontal Sweep Rates
The SECONDS/DIV s w i t c h selects cali brated sweep
r at e s for the
sweep
generator. The vari abl e control
p rov i d e s conti nuously variable sweep
rates
between t he
s
e
tt
i
n
g s
of
the
SECO N O S/OI V
switch. O nly when the
variable control is in it s fully clockwise position are the
sweep rates cali brated.
@
MAY 1980