OPERATING INSTRUCTIONS
17
MAGNIFIED SWEEP OPERATION
Since merely shortening the sweep time to magnify a portion
of an observed waveform can result in the desired portion
disappearing off the screen, magnified display should be
performed using magnified sweep.
Using the
POS
ition control, move the desired portion of
waveform to the center of the CRT. Pull out the
PULL X10
knob
to magnify the display ten times. For this type of display, the sweep
time is the
Time Base TIME/DIV
control setting
divided by 10. Rotation of the
POS
ition control can then be
used to select the desired portion of the waveforms.
X Y OPERATION
X Y
operation permits the oscilloscope to perform many
measurements not possible with conventional sweep operation.
The CRT display becomes an electronic graph of two
instantaneous voltages. The display may be a direct comparison
of the two voltages such as stereoscope display of stereo signal
outputs. However, the
X Y
mode can be used to graph almost
any dynamic characteristic if a transducer is used to change the
characteristic (frequency, temperature, velocity, etc.) into a
voltage. One common application is frequency response
measurements, where theY axis corresponds to signal amplitude
and the X axis corresponds to frequency.
1.
Depress the
X Y
switch and set the
Trigger Source
and
VERTical MODE
switches to
XY.
2.
In this mode, channel 1 becomes the X axis input and
channel 2 becomes the Y axis input. The X and Y
positions are now adjusted using the
POS
ition and
the
channel 2
POS
ition controls, respectively.
3.
Adjust the amount of vertical (Y axis) deflection with the
CH 2 VOLTS/DIV
and
VARIABLE
controls.
4.
Adjust the amount of horizontal (X axis) deflection with
the
CH 1 VOLTS/DIV
and
VARIABLE
controls.
VIDEO SIGNAL OBSERVATION
Setting the
COUPLING
switch to the
TV-H
or
TV-V
position permits selection of horizontal or vertical sync pulses
for sweep triggering when viewing composite video waveforms.
When the
TV-H
mode is selected, horizontal sync pulses are
selected as triggers to permit viewing of horizontal lines of video.
A sweep time of about 10 µs/div is appropriate for displaying
lines of video. The
VAR SWEEP
control can be set to display
the exact number of waveforms desired.
When the
TV-V
mode is selected, vertical sync pulses are
selected as triggers to permit viewing of vertical fields and
frames of video. A sweep time of 2 ms/div is appropriate for
viewing fields of video and 5 ms/div for complete frames (two
interlaced fields) of video.
At most points of measurement, a composite video signal is
of the () polarity, that is, the sync pulses are negative and the
video is positive. In this case, use ()
SLOPE.
If the waveform
is taken at a circuit point where the video wave-form is inverted,
the sync pulses are positive and the video is negative. In this
case, use
(+) SLOPE.
DIGITAL STORAGE OPERATION
Digitizing Repetitive Waveforms
While the most powerful feature of a digital storage
oscilloscope (DSO) is its ability to capture one-time events, a
DSO can also digitize conventional repetitive waveforms, such
as those observed on a standard analog scope.
An analog/digital unit such as the Model 2522C allows the
user to set up sensitivity, sweep, and triggering in a familiar
analog setting, and then switch to the digital mode. This is a
good way to gain familiarity with the digital features of the
instrument. You may wish to pursue this method as described
below in the “Refresh Mode” paragraph.
Also, some repetitive signals can be viewed and measured
much more effectively in the digital store mode than in the
analog mode. One example is slow signals below 60 Hz.
Signals that appear as a flickering waveform or just a moving dot
on the screen in the analog mode are displayed as a bright,
non-flickering, easily viewed entire waveform in the digital
store mode.
The digital store mode also improves viewing and meas-
urement of repetitive signals with low trigger repetition rates
relative to the sweep rate. In the analog mode, such
wave-forms may be too faint for viewing. In the digital store
mode, the display is equivalent to a CRT with infinite
persistence. The waveform can be easily viewed.
Refresh Mode
In the refresh mode, the waveform is digitized and displayed
on the screen. After the complete waveform is digitized, the
next trigger causes the stored waveform to be replaced
(refreshed) by a new waveform.
1.
Set up the oscilloscope to view a periodic waveform in
the
ANALOG
mode. Adjust the trigger,
VOLTS/DIV,
sweep
TIME/DIV,
and vertical position controls as
desired.
2.
Initially, disengage all of the digital storage control
switches (the group of switches beneath the CRT).
3.
Select digital storage operation by setting the
ANA-
LOG/STORAGE
switch to
STORAGE
(engaged).
When all digital storage control switches are released, the
“refresh” mode is selected. The waveform should appear
on the display, relatively unchanged from the previously
displayed analog version. In the “refresh” mode, the
display is continually updated as long as a suitable trigger
signal remains present.
