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Pulse Triggering
TDS 620A, 640A & 644A User Manual
3Ć113
H If you select Set to 50%, you cause the digitizing oscilloscope to search
for the point halfway between the peaks of the trigger source signal and
set the trigger level to that point.
When you select the pulse class Runt, the oscilloscope will trigger on a
short pulse that crosses one threshold but fails to cross a second threshold
before recrossing the first. To set up runt triggering:
1. Press TRIGGER MENU ➞ Type (main) ➞ Pulse (popĆup) ➞
Class (main) ➞ Runt (popĆup) ➞ Source (main) ➞ Ch1, Ch2, Ch3
(Ax1 on the TDS 620A), or Ch4 (Ax2 on the TDS 620A) (side). (See
Figure 3Ć58.)
2. Press Polarity (main) ➞ Positive, Negative,orEither (side).
3. Press Thresholds (main), and set the upper and lower thresholds for
runt detection with the side menu selections and the keypad or the
general purpose knob.
Polarity
Use this menu item to specify the direction of the runt pulse.
Press TRIGGER MENU ➞ Type (main) ➞ Pulse (popĆup) ➞
Class (main) ➞ Runt (popĆup) ➞ Polarity (main) ➞ Positive, Negative,or
Either (side).
H Positive looks for positiveĆgoing runt pulses.
H Negative looks for negativeĆgoing runt pulses.
H Either looks for both positive and negative runt pulses.
Runt Operation