Triggering on Waveforms
3–78
TDS 500B, TDS 600B, & TDS 700A User Manual
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 3–45: Main Trigger Menu — Runt Class
Set the Thresholds. 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 3–45. Triggering occurs at the
point the pulse returns over the first (lower) threshold going negative without
crossing the second threshold level (upper). The polarity selected in the Polarity
side menu determines the order that the threshold must be crossed for a runt
trigger to occur:
Positive requires that the lower threshold must be first crossed going positive,
then recrossed going negative without the upper threshold being crossed at all.
Negative requires that the upper threshold must be first crossed going negative,
then recrossed going positive without the lower threshold being crossed at all.
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