National Instruments NI USB-621x - Page 45

Chapter 4 Analog Input
© National Instruments Corporation 4-19 NI USB-621x User Manual
Figure 4-10. ai/SampleClock Too Fast
Figure 4-11. ai/ConvertClock Too Fast
Figure 4-12. ai/SampleClock and ai/ConvertClock Improperly Matched
• Sample Clock Too Fast for Convert Clock
ai/SampleClock
ai/ConvertClock
Sample #1 Sample #2 Sample #3
Channel Measured 1 2 3 0
1 2 3 0 1 2 3 0
• Sample Clock Pulses are Gated Off
• Convert Clock Too Fast for Sample Clock
• Convert Clock Pulses are Gated Off
ai/SampleClock
ai/ConvertClock
Sample #1 Sample #2 Sample #3
1230
12301230
Channel Measured
• Improperly Matched Sample Clock and Convert Clock
• Leads to Aperiodic Sampling
ai/SampleClock
ai/ConvertClock
Sample #1 Sample #2 Sample #3
1230
0
Channel Measured
1230