15
5.
In the
CHOP
sweep mode
(PULL CHOP
switch pulled
out), the sweep is chopped (switched) between channel 1
and channel 2. Using
CHOP,
one channel does not have
to “wait” for a complete swept display of the other channel.
Therefore, portions ofboth channel’s waveforms are
displayed with the phase relation-ship between the two
waveforms unaltered. Chop sweep is normally used for
low-frequency or low-speed waveforms at sweep times of
1 ms/div and slower; or where the phase relationship
between channel 1 and channel 2 requires measurement.
If chop sweep is used at sweep times of 0.2 ms/div and
faster, the chop rate becomes a significant portion of the
sweep and may become visible in the displayed waveform.
However, you may select chop sweep at any sweep time
for special applications.
6.
Adjust the channel 1 and 2
s t
POS
ition controls to place
the channel 1 trace above the channel 2 trace.
7.
Set the
CH 1
and
CH 2 VOLTS/DIV
controls to a
position that gives 2 to 3 divisions of vertical deflection
for each trace. If the display on the screen is
unsynchronized, refer to the “Triggering” paragraphs in this
section of the manual for procedures for setting triggering
and sweep time controls to obtain a stable display
showing the desired number of waveforms.
8.
When the
VERTical MODE
switch is set to
ADD,
the
algebraic sum of CH 1 + CH 2 is displayed as a single trace.
When the
PULL INV
switch is pulled out, the algebraic
difference of CH 1 – CH 2 is displayed.
9.
If two waveforms have no phase or frequency
relation-ship, there is seldom reason to observe both
wave-forms simultaneously. However, these oscilloscopes
do permit the simultaneous viewing of two such unrelated
waveforms, using alternate triggering. Refer to the
paragraphs on “Triggering — Trigger SOURCE Switch”
for details on alternate triggering.
TRIGGERING
The Model 2522C Oscilloscope provides versatility in sync
triggering for ability to obtain a stable, jitter-free display in
single-trace, or dual-trace operation. The proper settings
depend upon the type of waveforms being observed and the type
of measurement desired. An explanation of the various controls
which affect synchronization is given to help you select the
proper setting over a wide range of conditions.
AUTO or NORM Triggering
1. In the
AUTO
mode
(PULL NORM TRIG
pushed in),
automatic sweep operation is selected. In automatic sweep
operation, the sweep generator free-runs to generate a
sweep without a trigger signal. However, it automatically
switches to triggered sweep operation if an acceptable
trigger source signal is present. The
AUTO
mode is handy
when first setting up the scope to observe a waveform; it
provides sweep for wave-
form observation until other controls can be properly set.
Once the controls are set, operation is often switched back
to the normal triggering mode, since it is more sensitive.
Automatic sweep must be used for dc measurements and
signals of such low amplitude that they will not trigger
the sweep.
2. In the
NORM
mode
(PULL NORM TRIG
pulled out),
normal triggered sweep operation is selected. The sweep
remains at rest until the selected trigger source signal
crosses the threshold level set by the
TRIG LEVEL
control. The trigger causes one sweep to be generated,
after which the sweep again remains at rest until triggered.
In the normal triggering mode, there will be no trace
unless an adequate trigger signal is present. In the
ALT
VERTICAL MODE
of dual-trace operation with the
SOURCE
switch also set to
ALT,
there will be no trace
unless both channel 1 and channel 2 signals are adequate
for triggering. Typically, signals that produce even one
division of vertical deflection are adequate for normal
triggered sweep operation.
Trigger COUPLING Switch
1.
The
AC
position is used for most waveforms except
video. The trigger signal is capacitively coupled. Thus, it
blocks the dc component and references the average of the
“changing” portion of the waveform.
2.
The
TV H
and
TV V
positions are primarily for viewing
composite video waveforms. Horizontal sync pulses are
selected as trigger when the trigger
COUPLING
switch is
set to the
TV H
position, and vertical sync pulses are
selected as trigger when the trigger
COUPLING
switch
is set to the
TV V
position. The
TV H
and
TV V
positions may also be used as low frequency reject and
high frequency reject coupling, respectively. Additional
procedures for observing video waveforms are given later
in this section of the manual.
Trigger SOURCE Switch
The trigger
SOURCE
switch
(CH 1, CH 2,
etc.) selects the
signal to be used as the sync trigger.
1.
If the
SOURCE
switch is set to
CH 1
(or
CH 2)
the
channel 1 (or channel 2) signal becomes the trigger
source regardless of the
VERTICAL MODE
selection.
CH 1,
or
CH 2
are often used as the trigger source for
phase or timing comparison measurements.
2.
By setting the
SOURCE
switch to
ALT,
alternating
triggering mode is activated. In this mode, the trigger
source alternates between
CH 1
and
CH 2
with each
sweep. This is convenient for checking amplitudes,
waveshape, or waveform period measurements, and even
permits simultaneous observation of two wave-forms
which are not related in frequency or period. However,
this setting is not suitable for phase or timing comparison
measurements. For such measurements, both traces must
be triggered by the same sync signal. Alternate triggering
can only be used in dual-trace
