AppendixB DigitizerBasics
NI5911 User Manual B-10 ni.com
FigureB-8. DifficultPulse Train Signal
Ideally,the trigger event should occur at condition one, but sometimes
theinstrument may trigger on condition two because the signal crosses
thetrigger level. Youcan solve this problem without using complicated
signalprocessing techniques by using triggerhold-off,which lets you
specify a time from the trigger eventto ign ore additional triggers that
fallwithin that time. With an appropriate hold-off value, the waveform
in Figure B-8 can be properly captured by discarding conditions two
and four.
•Input coupling—Youcan configure the input channels on your
NI 5911 to be DC coupled or ACcoupled. DC coupling a llowsDC
and low-frequencycomponents of a signal to pass through without
attenuation. In contrast, ACcoupling removes DC offsets and
attenuates lowfrequency components of a signal. This feature can
be exploitedto z oom in on ACsignals with large DC offsets, such
asswi tching noise on a 12 V powersupply. Refer to Appendix A,
Specifications, for inputlimits that must be observed regardless of
coupling.
5V
+V
t
Hold-off Hold-off
12 34
1and 3 = Trigger Accepted
2and 4 = Trigger Ignored
TriggerLevel