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Appendix B Digitizer Basics
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National Instruments Corporation B-7 NI 5911 User Manual
Ideally, the trigger event should occur at condition one, but sometimes the
instrument may trigger on condition two because the signal crosses the
trigger level. You can solve this problem without using complicated signal
processing techniques by using trigger hold-off, which lets you specify a
time from the trigger event to ignore additional triggers that fall within that
time. With an appropriate hold-off value, the waveform in Figure B-6 can
be properly captured by discarding conditions two and four.
• Input coupling—You can configure the input channels on your
NI 5911 to be DC coupled or AC coupled. DC coupling allows DC and
low-frequency components of a signal to pass through without
attenuation. In contrast, AC coupling removes DC offsets and
attenuates low frequency components of a signal. This feature can be
exploited to zoom in on AC signals with large DC offsets, such as
switching noise on a 12 V power supply. Refer to Appendix A,
Specifications, for input limits that must be observed regardless of
coupling.
CBIHWum.book Page 7 Thursday, October 29, 1998 1:56 PM