Advanced Control Technologies SCOPE-TEST2 (PCC OSCILLOSCOPE ADAPTOR TOOLDUAL LEAD) - Manual (Page 3)

ADVANCED CONTROL TECHNOLOGIES, INC.
Indianapolis, Indiana 46278 (800) 886-2281
3
Scope-Test2
P/D 081399
BASIC TROUBLESHOOTING:
B. TEST EQUIPMENT:
Low to moderately priced oscilloscopes have limited, but usually sufficient, capabilities. While some units have their
highest voltage scale of 5 volts/division (with 10 vertical divisions on the screen) others may have their highest scales as
10 or even 20 volts/division. With an oscilloscope having a 20v/division scale, it is easy to see that the highest voltage that
could be displayed would be 200vpp (volts, peak-to-peak).
A sine wave of 339vpp (120 VAC) could not be shown fully on the screen if it were not for the availability of special test probes
which enable the scope to measure much higher voltages. A test probe labeled “X10” (which has no connection with the
X-10 protocol) does not mean that it amplifies the test voltage ten times, quite the reverse, it reduces the test voltage by
a factor of 10, or 1/10th. Therefore a 339vpp sine wave would be displayed on the oscilloscope screen as just under 40vpp.
This reduced voltage is much easier and safer for the scope to handle.
The horizontal part of the oscilloscope allows for the unit to display events that occur in very small slices of time. Typically,
a moderately priced unit will have gradations of sweep time from as long as one half second per division (the point will take
5 seconds to traverse the screen, 10 divisions, at .5sec/div.) to as short as one tenth of a micro-second (.1m sec) per division
(the entire screen will display an event that occurs in the span of one millionth of a second).
Neither the slowest, nor the fastest sweep settings would be appropriate to view a single 60Hz sine wave. One cycle of
a 60Hz sine wave occurs in 16.66 ms (thousandths of a second). Setting the sweep time for 2ms/div. means the display
shows an event which is 20 milli-seconds in duration. That means that there is room for one full cycle, 16.66 ms, plus about
a quarter of the next cycle.
For most situations, this is
more than sufficient, however,
since most oscilloscopes have
both coarse and fine sweep
adjustments, they can be set
to show only one full cycle if
the technician desires. In order
to display a single cycle, the
oscilloscope sweep time can
be set for 1ms/div. and then
fine adjusted to show a single
sine wave.
5 volts/div.
Coarse setting = 1 ms/div, fine adjustment
to allow for one sine wave.
About 40
volts peak
to peak
About 16.66 ms
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(Page 74, PCC Reference Manual)