User Manual

Tr igger 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, o r not equal to a set time period (width).
A r unt pulse is a pulse that crosses one threshold level but fails to cross a second threshold before recrossing the first.
Therefore, a runt trigger needs two threshold l evels to define the two levels that a signal must pass through to be considered
a valid (nonrunt) signal. (See page 27, Available trigger types.)
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 Mu
ltipurpose 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 s
ource, 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,
negativ
e, or either) to trigger on.
6. Push the Thresholds side-menu button and use the Multipurpo se knob to select and click the trigger levels (thresholds) to
use to d
etect a runt pulse:
Click High and use the M ultipu rpo se knob to manually set the level that defines a v alid high signal threshold level.
Click Low and use the Multipurpose knob to manually set the level that defines a valid low signal threshold l evel.
Clic
k Choose Preset and use the Multipurpose knob to set the trigger threshold levels to predefined signal logic family
levels (TTL, CMOS, ECL, and so on) or to 0.
7. Pus
htheTrigger When side-menu button and use the Multipurp ose knob to select and click Runt Occurs to trigger on
any runt event. If triggering on a runt width, use the Multip urpose knob to select and click the runt pulse width condition to
test for, and enter the r unt width time parameter.
38 TBS2000 Series User Manual