Measurement Computing ADAC-LVi User Manual

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Chapter 2 Easy Analog Input VIs

ADAC LabVIEW VI

The Advanced AI Continuous Async Occurrence example demonstrates the use of
ADAC OccurrenceConfig VI. The example shows how to use multiple occurrences for a
continuous asynchronous acquisition. This is a timed acquisition, meaning that a
hardware clock is used to control the acquisition for fast and accurate timing. It is also a
continuous circular buffered acquisition. This means that a software buffer is used
between your DAQ board and LabVIEW. While data is being transferred from your
board into one of the input buffers, LabVIEW is reading data from another buffer. The
occurrence VI makes the acquisition asynchronous (allowing processor time for other
things to run) by causing the loop to sleep until notified a buffer is available which is then
read into LabVIEW.

The Advanced AI AboutTrigger Async Occurrence example demonstrates the use of
ADAC OccurrenceConfig VI with ABOUT TRIGGER mode enabled. Currently the 5400
and 5800 series boards are the only ADAC boards the support ABOUT TRIGGER mode.
The example VI demonstrates how to use the Intermediate Analog Input VIs to capture
data before and after a trigger. Once started data in continuously collected into a buffer
until a trigger is received. The number of samples obtained after a trigger is "Post Trigger
Samples" and the number of samples obtained before the trigger is "BufferSize (minus)
Post Trigger Samples". The starting point for pre-trigger data is indicated in the BUFFER
STATUS cluster as TriggerPointPre and the post-trigger data as TriggerPoint. If a buffer
has not been filled before the trigger occurs the Buffer Status flag is set to 2 and the
BufferWrite is set to the number of pre-trigger samples actually obtained.

This VI also shows how to use multiple occurrences for a continuous asynchronous
acquisition. This is a timed acquisition, meaning that a hardware clock is used to control
the acquisition for fast and accurate timing. It is also a continuous circular buffered
acquisition. This means that a software buffer is used between your DAQ board and
LabVIEW. While data is being transferred from your board into one of the input buffers,
LabVIEW is reading data from another buffer. The occurrence VI makes the acquisition
asynchronous (allowing processor time for other things to run) by causing the loop to
sleep until notified a buffer is available which is then read into LabVIEW.

The Advanced AI PreTrigger Async Occurrence example demonstrates the use of
ADAC OccurrenceConfig VI with PRE TRIGGER mode enabled. Currently the 5400
and 5800 series boards are the only ADAC boards the support PRE TRIGGER mode.
The example VI demonstrates how to use the Intermediate Analog Input VIs to capture
data before a trigger. Once started data in continuously collected into a buffer until a
trigger is received. The number of samples obtained before the trigger is the actual Buffer
Size. If a buffer has not been filled before the trigger occurs the Buffer Status flag is set
to 2 and the BufferWrite is set to the number of pre-trigger samples actually obtained.