Figure 4-10. pretriggered data acquisition example, Ai sample clock signal, Ai sample clock signal -15 – National Instruments NI 6238 User Manual
Page 41
Chapter 4
Analog Input
© National Instruments Corporation
4-15
example, four. The value decrements with each pulse on ai/SampleClock,
until the value reaches zero. The sample counter is then loaded with the
number of posttriggered samples, in this example, three.
Figure 4-10. Pretriggered Data Acquisition Example
If an ai/ReferenceTrigger pulse occurs before the specified number of
pretrigger samples are acquired, the trigger pulse is ignored. Otherwise,
when the ai/ReferenceTrigger pulse occurs, the sample counter value
decrements until the specified number of posttrigger samples have been
acquired.
NI 6238/6239 devices feature the following analog input timing signals.
•
•
AI Sample Clock Timebase Signal
•
•
AI Convert Clock Timebase Signal
•
•
•
•
AI Sample Clock Signal
Use the AI Sample Clock (ai/SampleClock) signal to initiate a set of
measurements. Your M Series device samples the AI signals of every
channel in the task once for every ai/SampleClock. A measurement
acquisition consists of one or more samples.
n/a
0
1
2
3
1
0
2
2
2
ai/StartTrigger
ai/ReferenceTrigger
ai/SampleClock
ai/ConvertClock
Scan Counter