Tektronix TPS2000 Series User Manual page 77

For example, if you want to find the cause of a glitch in your test
circuit, you might trigger on the glitch and make the pretrigger
period large enough to capture data before the glitch. You can then
analyze the pretrigger data and perhaps find the cause of the glitch.
You change the horizontal scale of all the waveforms by turning the
SEC/DIV knob. For example, you might want to see just one cycle
of a waveform to measure the overshoot on its rising edge.
The oscilloscope shows the horizontal scale as time per division in
the scale readout. Since all active waveforms use the same time
base, the oscilloscope only displays one value for all the active
channels, except when you use Window Zone. For information on
how to use the window function, refer to page 9- - 23.
For oscilloscope-specific descriptions, refer to page 2- - 9 in the
Operating Basics chapter and page 9- - 21 in the Reference chapter.
Time Domain Aliasing. Aliasing occurs when the oscilloscope does not
sample the signal fast enough to construct an accurate waveform
record. When this happens, the oscilloscope displays a waveform
with a frequency lower than the actual input waveform, or triggers
and displays an unstable waveform.
Actual high-frequency
Apparent low-frequency
waveform due to aliasing
TPS2000 Series Digital Oscilloscope User Manual
waveform
Sampled points
Understanding Oscilloscope Functions
3- 9