Operating instructions

Operating
Instructions--71387
The
AQS stored
single-sweep display
is effectively 1000
times slower
than the real-time
display ; however, the
ACQUIRE-STOP
DELAY time
(post-trigger time) remains
unchanged
and becomes
insignificant compared to
the
digitized
sweep . Therefore,
the stored
single-sweep
display is
for practical
purposes all pretrigger
.
During single-shot
acquisition with an
external clock
input the
7854 may not
necessarily sample one data
point for each clock pulse, as
shown below . -
NOTE
3 . EXT/AQR
(EXT CLOCK IN)----This
mode connects
the
external
TTL compatible clock
signal, applied to the front-
panel EXT
CLOCK IN connector,
to the companion
digitizing
oscilloscope
mainframe (7854) .
The real-time
display is the same
as the internal mode
with the
intensified zone and
associated ACQUIRE-STOP
DELAY readout corresponding
to post-trigger time in the
subsequent
stored
single-sweep display . When the
AQS
(acquire single-shot)
display is stored,
the ACQUIRE-
STOPDELAY time
is as displayed on the
readout but the
effective TIME/DIV of
the display changes at a
rate
determined by the
frequency of the external
clock signal .
The resulting
TIME/DIV for the stored
single-sweep
display acquired
in the external clock
mode can be
determined by
the following
formula :
or
EXT TIME/DIV
= 102 .4 x External
Clock Period
_
102 .4
x
- EXT CLOCK
1
1FREQUENCY
NOTE
The 7854
may not return from the
acquire single-shot
(AQS)
mode if the acquire-stop
occurs before the
memory is filled once .
This is most noticeable
at slow
sweep speeds,
especially in the internal
: 1000 clock
mode . When
the 7854 AQS button
is pressed, the
7854 begins
to sample the
waveform and fill the
memory . The acquire-stop signal
occurs at a set
interval
after the 7887 is
triggered, - this interval is
the
acquire-stop delay
time . if the acquire-stop
is
generated before the
7854 has filled the
memory
once (one digital
sweep) the 7854 will
notrecognize
it, and the
system will keep on
digitizing .
When the
7854 is used
for non-single-sweep
acquisition
(AQR), the
71387 clock should
be disabled by
selecting the
EXT/AQR
pushbutton
and removing any
connection from
the
EXT CLOCK IN
connector . This prevents the
71387
clock
signal from interfering
with the 7854
acquisition
mode .
To obtain a
stored single-sweep
display of a repetitive
signal with a
7854 digitizing
oscilloscope, first obtain a
real-time display
(7854 set to Scope
CRT Display Mode)
in the
NORM TRIGGERING
MODE . Then select the
portion of
pretrigger and post-trigger
desired for the
subsequent
stored single-sweep
display with
the
ACQUIRE-STOP DELAY
control . The displayed intensified
zone
relates to the portion of
the single-sweep displayed
after
the single-sweep
trigger event (post-trigger)
and the
non-intensified zone
relates to the portion
of single-
sweep displayed
before the single-sweep
trigger event
REV A MAR 1981