Stability Control - Tektronix 545A Instruction Manual

Operating
Instructions
—
Type 545A
waveform.
This
is
done
through simultaneous
use of
Time
Base
A
and
Time Base
B. In this
application
Time
Base B
is
used
to
provide
the accurate time delay while Time
Base
A
presents
a
normal
horizontal
sweep
at
the end
of the delay period.
The
duration of the
sweep
delay
is
controlled
by
the
Time
Base
B
TIME/CM
OR
DELAY
TIME
switch
and
the
DELAY-TIME
MULTIPLIER
control.
The delayed sweep
feature
of the
Type 545A
Oscilloscope
can be used
in
a
number
of special applications
to increase
the versatility of the instrument. Such applications include
high magnification
of a selected portion of
an undelayed
sweep, accurate time measurements, and
accurate
meas-
urements
of
waveform
jitter.
Also,
it
is
possible
to
pick
off
and
display
any
desired
line
of a
television
scan or to
check
pulse-time
modulation.
In
addition, the delayed
sweep
feature
is
readily
adaptable
to a great
number
of
other applications.
The delayed
sweep
is
selected
when
the
HORIZONTAL
DISPLAY
switch
is
in
the
'A'
DEL'D BY
B'
position.
The
amount
of
delay
occurring
from
the application
of the
triggering
waveform
until
the
sweep
runs
is
indicated
di-
rectly
by the
settings
of the
TIME/CM
OR
DELAY TIME
switch
and
the
DELAY TIME
MULTIPLIER
control.
The
settings
of the
two
controls are
multiplied together
to
obtain the
actual delay
time.
For example,
if
the
TIME/CM
OR
DELAY
TIME
switch
is
set
at
1
MILLISEC and
the vernier
dial
of
the
DELAY
TIME MULTIPLIER
control
indicates
6.75,
the
delay
time
is
6.75
milliseconds.
When
the
Time
Base
A
STABILITY
control
is
in
the
fully
clockwise
position, the
horizontal
sweep
starts
immediately
at the
completion
of the
delay
period
at
a
rate
determined by
the settings of the
Time Base
A TIME/CM
controls.
There are
actually
two modes
of
delayed
sweep
opera-
tion
available
in
the
Type 545A
Oscilloscope
(see
Figure
2-11).
In
one
mode
the
delayed sweep
is
started
immedi-
ately
after
the completion
of the
delay
time. This
is
the
mode
described previously
and
is
obtained
with the
Time
Base
A
STABILITY
control
fully
clockwise.
This
mode
permits
you
to select
continuously variable delay
times
and
is
the
mode
of
operation used
to
make
accurate time
and waveform
jitter
measurements
as
well
as
most
other
measurements.
The second delayed-sweep
mode
is
different
from
the
first in
that the
sweep
does not
start at the
completion
of
the
delay time
until
a
triggering
waveform
is
applied
to
Time Base
A.
The
delay time
in this
mode
is
not continu-
ously variable
and
is
dependent
not only on
the settings of
CASE
1
:
A'
STABILITY
CONTROL
FULLY
CLOCKWISE
DELAYED SWEEP PRESENTATION
TO
10
SECONDS)
CASE
2: A'
STABILITY
CONTROL
SET
FOR TRIGGERED
OPERATION
DELAYED SWEEP PRESENTATION
(VARIABLE
FROM
1
MICROSECOND
TO
10
SECONDS!
Fig.
2-11.
Comparison
of the
two delayed-sweep modes.
In
each case
the
waveform shown
represents the input to the oscilloscope.
The
waveform shown
in
the
delayed-sweep
presentation boxes represents the
portion of the input
waveform
that
is
actually displayed
on
the
oscilloscope screen. Note that
in
Case 2 an additional triggering pulse
is
required before
the
delayed
sweep
will occur.