National Instruments PCI-6251 User Manual

C-2 | ni.com
Appendix C Troubleshooting
How can I use the AI Sample Clock and AI Convert Clock signals on an M Series device
to sample the AI channel(s)?
M Series devices use AI Sample Clock (ai/SampleClock) and AI Convert Clock
(ai/ConvertClock) to perform interval sampling. As Figure C-1 shows, AI Sample Clock
controls the sample period, which is determined by the following equation:
1/sample period = sample rate
Figure C-1. AI Sample Clock and AI Convert Clock
AI Convert Clock controls the convert period, which is determined by the following equation:
1/convert period = convert rate
This method allows multiple channels to be sampled relatively quickly in relationship to the
overall sample rate, providing a nearly simultaneous effect with a fixed delay between channels.
Analog Output
I am seeing glitches on the output signal. How can I minimize it?
When you use a DAC to generate a waveform, you may observe glitches on the output signal.
These glitches are normal; when a DAC switches from one voltage to another, it produces
glitches due to released charges. The largest glitches occur when the most significant bit of the
DAC code changes. You can build a lowpass deglitching filter to remove some of these glitches,
depending on the frequency and nature of the output signal. Visit
ni.com/support for more
information about minimizing glitches.
Channel 0
Channel 1
Convert Period
Sample Period

National Instruments PCI-6251 Specifications

General

Brand	National Instruments
Model	PCI-6251
Category	I/O Systems
Language	English