Trigger setup
Triggering on a runt pulse
Use this procedure to set the oscilloscope to trigger when a runt pulse occurs. You can also trigger when a runt pulse is less
than, greater than, equal to, or not equal to a set time period (width).
A runt pulse is a pulse that crosses one threshold level but fails to cross a second threshold before recrossing the
fi
rst.
Therefore, a runt trigger needs two threshold levels to de
fi
ne the two levels that a signal must pass through to be considered
a valid (nonrunt) signal. (See page 27,
Runt pulse triggering is most often used to troubleshoot or analyze digital signals.
The minimum runt pulse width setting is 1 ns.
1.
Push the
Trigger Menu
front-panel button.
2.
Push the
Type
side-menu button.
3.
Use the
Multipurpose
knob to select and click
Runt
.
4.
Push the
Source
side-menu button and use the
Multipurpose
knob to select and click the channel to use as the trigger
signal source, or select
AC Line
to use the AC power source frequency as the trigger signal.
5.
Push the
Polarity
side-menu button and use the
Multipurpose
knob to select and click the runt pulse polarity (positive,
negative, or either) to trigger on.
6.
Push the
Thresholds
side-menu button and use the
Multipurpose
knob to select and click the trigger levels (thresholds) to
use to detect a runt pulse:
Click
High
and use the
Multipurpose
knob to manually set the level that de
fi
nes a valid high signal threshold level.
Click
Low
and use the
Multipurpose
knob to manually set the level that de
fi
nes a valid low signal threshold level.
Click
Choose Preset
and use the
Multipurpose
knob to set the trigger threshold levels to prede
fi
ned signal logic family
levels (TTL, CMOS, ECL, and so on) or to 0.
7.
Push the
Trigger When
side-menu button and use the
Multipurpose
knob to select and click
Runt Occurs
to trigger on
any runt event. If triggering on a runt width, use the
Multipurpose
knob to select and click the runt pulse width condition to
test for, and enter the runt width time parameter.
38
TBS2000 Series User Manual
