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
POSition 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
POSition 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 opera-
tion. The CRT display becomes an electronic graph of two
instantaneous voltages. The display may be a direct com-
parison 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 fre-
quency response measurements, where the Y 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 X
−
Y.
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
POSition and
the channel 2
POSition 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 con-
trols.
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
µ
s/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 2522B 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 dis-
played on the screen. After the complete waveform is digit-
ized, 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
i n t h e ANALOG mo de. A djust the trigger,
VOLTS/DIV, sweep TIME/DIV, and vertical posi-
tion 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.
OPERATING INSTRUCTIONS
15