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Triggering on Waveforms
TDS 500C, TDS 600B, & TDS 700C User Manual
3–99
Set to Trig When. The oscilloscope compares the pulse edge of the trigger source
against the slew rate setting read out in the Trigger When menu. To select
whether to trigger on edges with slew rates faster than or slower than that
indicated in readout, do the following step:
Press TRIGGER MENU ➞ Type (main) ➞ Pulse (pop-up) ➞ Class (main) ➞
Slew Rate (pop-up) ➞ Trigger When (main) ➞ Trigger if Faster Than or
Trigger if Slower Than (side). (See Figure 3–48.)
NOTE. If you select Trigger if Faster Than and the oscilloscope does not trigger,
it may be because the pulse edge is too fast rather than too slow. To check the
edge speed, switch to edge triggering. Then trigger on the pulse edge and
determine the time the edge takes to travel between the levels set in the slew rate
Thresholds menu. The oscilloscope cannot slew rate trigger on pulse edges that
traverse between threshold levels in 600 ps or less.
Also, to reliably slew rate trigger, a pulse must have a width of 7.5 ns or more. A
pulse of less width may trigger on the wrong slope or not trigger at all. Switch to
edge triggering and check the pulse width if you can’t slew rate trigger as
expected.
To understand what happens when you slew rate trigger, study Figure 3–48 as
you consider the following points:
H The main menu shows the oscilloscope is set to trigger based on the slew
rate of a pulse input to the trigger source, Ch 1. It is set to monitor the
positive-polarity pulse edges of the trigger source and to trigger on any edge
with a slew rate faster than the slew rate setting.