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Pulse Triggering
TDS 620A, 640A & 644A User Manual
3Ć115
H Regardless of the polarity setting, triggering occurs at the point the runt
pulse recrosses its first threshold.
When you select the pulse class Width, the oscilloscope will trigger on a
pulse narrower (or wider) than some specified range of time (defined by the
upper limit and lower limit).
Polarity
To define whether the pulses are positive or negative:
Press TRIGGER MENU ➞ Type (main) ➞ Pulse (popĆup) ➞
Class (main) ➞ Width (popĆup) ➞ Polarity (main) ➞ Positive or Negative
(side).
Trig When
This menu item lets you establish the range of widths (in units of time) the
trigger source will search for and whether to trigger on pulses that are
outside this range or ones that fall within the range.
1. Press TRIGGER MENU ➞ Type (main) ➞ Pulse (popĆup) ➞
Class (main) ➞ Width (popĆup) ➞ Trig When (main).
2. Press Within Limits (side) if you want the oscilloscope to trigger on
pulses that fall within the specified range. If you want it to trigger on
pulses that are outside the range, then press Out of Limits (side).
3. To set the range of pulse widths in units of time, press Upper Limit
(side) and Lower Limit (side). Enter the values with the general purpose
knob or keypad. The Upper Limit is the maximum valid pulse width the
trigger source will look for. The Lower Limit is the minimum valid pulse
width. The oscilloscope will always force the Lower Limit to be less than
or equal to the Upper Limit.
Level
To set the trigger level with the Level main menu:
Press TRIGGER MENU ➞ Type (main) ➞ Pulse (popĆup) ➞
Class (main) ➞ Width (popĆup) ➞ Level (main) ➞ Level, Set to TTL, Set to
ECL,orSet to 50% (side).
See Triggering, on page 2Ć13.
See Triggering, on page 3Ć132.
Width Operation
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