National Instruments Data Acquisition Device E Series - Manual (Page 48)

Chapter 2 Analog Input
© National Instruments Corporation 2-15 E Series User Manual
AI Start Trigger Signal
You can use the AI Start Trigger (ai/StartTrigger) signal to begin a
measurement acquisition. A measurement acquisition consists of one or
more samples. If you do not use triggers, you begin a measurement with a
software command. Once the acquisition begins, you can configure the
acquisition to stop when one of the following conditions apply:
• When a certain number of points are sampled (in finite mode)
• After a hardware reference trigger (in finite mode)
• With a software command (in continuous mode)
Using a Digital Source
To use ai/StartTrigger with a digital source, specify a source and an edge.
The source can be an external signal connected to any PFI or RTSI <0..6>
pin. The source can also be one of several internal signals on your DAQ
device. Refer to Device Routing in MAX in the NI-DAQmx Help or the
LabVIEW 8.x Help for more information.
Also, specify whether the measurement acquisition begins on the rising
edge or falling edge of the ai/StartTrigger signal.
Figure 2-4 shows the timing requirements of the ai/StartTrigger source.
Figure 2-4. ai/StartTrigger Source Timing Requirements
Using an Analog Source
When you use an analog trigger source, the acquisition begins on the first
rising edge of the Analog Comparison Event signal. Refer to the
Triggering
with an Analog Source section of Chapter 10, Triggering , for more
information on analog trigger sources.
Rising-Edge
Polarity
Falling-Edge
Polarity
t
w
t
w
= 10 ns minimum