35
2.2.7.
Use of the alternate
time-base |S2)
The
PM 3266
is
equipped
with
display
switching.
This
offers
the
instrument
user
a
simultaneous
display
of the
signal
on the
two
time
scales
provided
by
the main
time-base
and
by the delayed
time-base.
Detailed
examination
of
a certain
portion
of the
main
time-base
display
is
enabled
by
expanding
the
time
interval
of
interest
by means
of the
delayed
time-base.
Expansion
is achieved
by
selecting
a
correspondingly
faster
sweep
for
the
delayed
time-base
TIME/div.
control.
Positioning
of
the
time
interval
is
set by the
DELAY
TIME
potentiometer.
The
part of
the
signal
under
detailed
observation
by the
delayed
time-base
remains
as an
intensified
portion
of
the
main
time-base
display.
This
not
only
facilitates
the
location
of the
required
detail
during
dialling
but also
serves
as a visual
indication
of which
portion of
the overall
trace
is
being
examined.
One
can
immediately
correlate
the
detail
with the
overall
signal,
which
may be
extremely
complex,
without
the
necessity
of
switching
between
MAIN
TB
and DEL'D
TB.
Vertical
shift
between
the
two
time-base
displays is
continuously
variable
with the
TRACE
SEParation
control
(R6).
2.2.8.
Use
of the
3rd channel
trigger
view
2.2.8.
1.
External
or Internal
triggering
In many
applications
such
as
triggering
with
digital signals or signals
of widely differing
forms,
it is necessary
to use an
external
trigger source
to ensure
proper
timing
relationships
and
to
know
the time
relationship of
the
trigger
signal and
the measuring signal(s).
By depressing
the TRIG VIEW
push-button, the external
trigger
signal (fed
to
input
socket X7)
is displayed
as a third
channel with
the threshold
near
the horizontal
central
graticule
line.
By adjusting
the LEVEL/SLOPE
(R7,
S7) control,
it is easy to determine which
part
of the
trigger
signal
is initiating
the
sweep.
This is also possible
for signals
internally derived
from
the A or B
channel
when
push-button
A
or B of switch
S22 is
depressed.
The sensitivity
control of
the
external trigger view mode
has two steps,
bU
mV/div
and
0,5
V/div.
With the
push-button switch EXT
(S22)
depressed the deflection factor
is
100 mV/div
which is compatible
with ECL levels.
In the
mode
EXT
-r
10
(S22)
the
deflection factor is
1
V/div which
is compatible
with TTL levels.
2. 2.
8. 2.
Single
shot
With control LEVEL/SLOPE
(R7,
S7)
the
trigger
level
can be set at
a
predetermined value
without the need
of an input
signal. This
is
of importance
when the signal to be
measured
is not available in advance
as
when
single events are under test. When
input signals, which surpass
a
known threshold,
have to be
displayed,
the
trigger level (R7,
S7) can be set in advance and an input signal of sufficient
amplitude will
initiate the time-
base sweep.
The procedure
to set the trigger level is as follows: Depress
push-button
TRIG VIEW.
Position the trace
by
means of the
LEVEL
(R7) control so many divisions in opposite direction
(in
relation
to
the horizontal
central
graticule line)
as
the
trigger threshold is
required.
Note:
The trigger threshold
is
defined
as
the distance
between the
triggerpoint and the zero line of
the
amplifier (i.e. without input signals and deflection by
means
of POSITION controls).
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