Pulse Triggering
TDS 420A, TDS 430A, TDS 460A & TDS 510A User Manual
3–95
Selected Trigger Bar at
Upper Threshold
Runt Pulse Crosses First Threshold
Only, Recrosses First Threshold
Level, and Triggers Acquisition
Unselected Trigger Bar
at Lower Threshold
Figure 3–50: Main Trigger Menu—Runt Class
To set the two threshold levels used in detecting a runt pulse:
1. Press TRIGGER MENU
➞ Type (main) ➞ Pulse (pop-up) ➞
Class
(main) ➞ Runt (pop-up) ➞ Thresholds (main).
2. Use the general purpose knob or keypad to set the values for the high and
low thresholds.
Hint: To use the Trigger Bar feature to set the threshold levels on the pulse train,
press DISPLAY
➞ Readout Options (main) ➞ Trigger Bar Style (side) until
Long appears in that menu item.
Note the position of the trigger indicator in Figure 3–50. Triggering occurs at the
point the pulse returns over the first (lower) threshold going negative without
crossing the second threshold level (upper). Be aware of the following consider-
ations when using Runt triggering:
When Positive is set in the Polarity side menu, the lower threshold must be
first crossed going positive, then recrossed going negative without crossing
the upper threshold at all.
When Negative is set in the Polarity side menu, the upper threshold must be
first crossed going negative, then recrossed going positive without crossing
the lower threshold at all.
Thresholds
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