Buffered DAQ with Conditional Retrieval

[Sirok]

I am in the process of evaluating LabView 2011. Back with LabView 6.1, using Traditional DAQ, there was an analog triggered DAQ example that I used as the basis for several DAQ Vis:

The Vi “retrieves the specified amount of data from one or more analog input channels when a software analog trigger occurs.  This is a timed acquisition, meaning that a hardware clock is used to control the acquisition rate for fast and accurate timing.  It is also a buffered acquisition, meaning that the data are stored in an intermediate memory buffer after they are acquired from the DAQ board.  Since this VI uses a software analog trigger, data are continuously acquired with LabVIEW checking the intermediate buffer for the analog trigger specifications to be met.  Once met, this VI retrieves and displays data from that buffer after the appropriate amount of data (before and after the trigger) have been acquired.  The vertical cursor on the graph indicates where the trigger occurred. Use this VI to wait for a software analog trigger, acquiring a relatively small amount of data (it must fit in the memory available), where each point does not need to be viewed or processed while it is being acquired.”

It used AI Config, to set the buffer size; AI Start to set Continuous Acquisition; AI Read (calling AI Buffer Read) to set Conditional retrieval and set the trigger level for the analog channel with pre and post trigger specifications.

 This would essentially wait for the analog channel to reach the trigger threshold and return the pre and post trigger data. I used this routine with E series boards including the DAQCard-6024E.

I don’t see this type of DAQ example with LabView 2011 and DAQmx. Is this type of buffered triggered acquisition available for the DAQCard-6024E or the cDAQ (cRIO-9215)? When I run DAQ Assistant with either of these boards, I see only a Digital triggering option.

With these devices, do I have to do my own buffering and triggering routine in LabView? Are there any cDAQ analog input modules or other cards that support analog triggering?

[Jacob_R]

Hello!

I did not find an example of that in the example finder, however there is a great example you can follow from our Developer Zone regarding start and reference triggers. This example does not use Express VI's though. To be able to control the buffer size, I would suggest using the DAQmx VI's instead. Using the Timing VI you can control the buffer size using the samples per channel property. You can also specify the start and reference triggering to control the pre-trigger and post-trigger samples acquired.

You will not be able to do AI triggering with the 9215, however you can do it with the 9205 and 9206. Check out this link for more information; I sent you a private message if you are interested in these modules. This may also be possible with your 6024E, depending on the boards you are using.

Hope that helps,