3.
The rolling display can be frozen at any time by
pressing the SAVE CH2 or SAVE ALL switches (as
discussed in the section on “Digitizing Repetitive
Waveforms”).
NOTE
ROLL mode cannot be used on sweep
speeds greater than 10 ms/div.
Expanded Sweep Settings—SLOW X100 Mode
In digital mode, the 10 ms/div to 0.5 s/div TIME/DIV
ranges can be expanded by a factor of 100 by depressing the
SLOW X100 switch. For example, the 10 ms/div setting
becomes 1000 ms (1 sec)/div when this switch is engaged.
This time base expansion is extremely useful for observing
very slow events. With it, the scope is capable of recording
an event up to 500 seconds in duration (.5 sec/div x100
becomes 50 sec/div).
Using Plotter Output
The Model 2522B oscilloscope provides facilities for
driving an analog plotter. The following instructions explain
how to output a waveform; however, since plotters vary
greatly, only general instructions have been given. Consult
the manual for the particular plotter for more specific in-
structions. Also, it is recommended that you read this entire
procedure first, because some steps may need to be per-
formed in a different sequence, depending on the plotter.
1.
Initially, se the PLOT switch to “off” (released).
2.
Use any of the digital modes described above to obtain
a digitized display to be plotted. Once the desired
display is obtained, freeze it using the SAVE ALL
switch.
3.
Connect the plotter’s Y (vertical) input to either the
CH1 or CH2 OUTPUT jack on the rear panel of the
oscilloscope, depending on which channel display you
wish to plot.
4.
Connect the plotter’s pen lift control input to the PEN
DOWN output jack on the rear of the scope.
5.
Momentarily disable external up/down control of the
plotter pen; that is, set the pen to be permanently lifted
from the paper surface. This will allow you to exercise
initial “trial and error” sweeps without using up exces-
sive ink. Consult the manual for the particular plotter
for details.
6.
Engage the PLOT switch. This will gate a TTL-level
square wave through to the PEN DOWN output jack.
The repetition rate of this square wave is controlled by
the front panel TIME/DIV control. The relationship
is as follows. Each low or high portion of the square
wave represents the output of one screen, i.e. ten
divisions of waveform (10.24 divisions to be more
exact). This output takes place at a rate that is 1/10th
that of the TIME/DIV setting. For example, if the
TIME/DIV setting is 10 ms/div, the plotter output
sends out waveform information at a rate of
100 ms/div. For the full 10.24 divisions of screen, this
means a total interval of 1.024 seconds. Thus, the
square wave has low and high portions that are each
1.024 seconds long. The PEN DOWN indicator on the
front panel of the oscilloscope lights during each low
portion.
NOTE
Though many plotters use a TTL-low level
as the “pen down” signal, and technically
only require plotting information during
that low portion, this oscilloscope outputs
a full screen of data on both the low and
high intervals of the square wave. This
discussion assumes a plotter using TTL low
as the “pen down” command.
When the PLOT switch is released, the
PEN DOWN output is at a constant TTL
high.
Engaging the SLOW X100 switch slows
the plot output by a factor of 100 on the
10 ms/div to 0.5 S/div TIME/DIV ranges.
7.
With the plotter’s pen control input still disabled,
observe the PEN DOWN indicator on the scope to
determine the repetition rate of the square wave. Ad-
just as desired using the TIME/DIV control. It will be
necessary to use the plotter’s own time base to move
its pen in the horizontal (X) direction. If possible, set
that movement to begin on the high-to-low transition
of the PEN DOWN signal. Through trial and error,
with the pen still up, run the plotter horizontally to
determine the speed that produces the desired plot
width during the PEN DOWN interval as observed on
the LED. Also adjust the vertical deflection and offset
for the desired height.
8.
Finally, during the high portion of the square wave
(PEN DOWN indicator off), re-enable external pen
control on the plotter. At the next transition of PEN
DOWN to low, the plotter should produce the desired
results.
NOTE
If you are unable to trigger the horizontal
plotter sweep from the PEN DOWN sig-
nal, you may have to enable that sweep
manually using the PEN DOWN indicator
as a timing guide.
APPLICATIONS GUIDEBOOK
B+K Precision offers a “Guidebook to Oscilloscopes”
which describes numerous applications for this instrument
and important considerations about probes. It includes a
glossary of oscilloscope terminology and an understanding
of how oscilloscopes operate. It may be downloaded free of
charge from our Web site, www.bkprecision.com.
OPERATING INSTRUCTIONS
17