When use DAQmx Configure Input Buffer.vi as in Q6 HW CLAD Prep Guide appears

[jesLVbcn]

Hello,

Not clear when to use DAQmx Configure Input Buffer.vi as appears in Q6 Hardware Section in CLAD Prep Guide LabVIEW 2017. I can understand that you need a buffer when you acquire continuously but there are others DAQmx VIs in the guide that acquire also continuously without this DAQmx VI Buffer.

Thank You!

[crossrulz · Accepted solution]

The important thing here is that you have two tasks running in the same loop.  In order for both of them to never error due to a buffer overrun, the reads need to capture the same amount of time's worth of data.

So looking at the bottom task we have a sample rate of 10kS/s and we are reading 10k samples with each iteration of the loop.  Do the math and we get 1 second of data (10kS / 10kS/s = 1s).

Now we look at the top task.  It has a sample rate of 10S/s.  Multiply that by the 1s of data that we need (as calculated from the bottom task) and we find we need to read 10 samples per iteration.  Giving the answer of A.

[jesLVbcn]

Thanks for your answer. I wonder if this VI will do the same task and have the same performance without the DAQmx Configure Input Buffer. 

It works using LabVIEW and running the VI without the buffer.

[crossrulz]

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@jesLVbcn wrote:

I wonder if this VI will do the same task and have the same performance without the DAQmx Configure Input Buffer. 

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Well, I think that the buffer sizes are actually being overwritten by the DAQmx Timing.vi.  I would have to do some experiments to verify that.  Regardless, the important thing is to keep up with your data so that the buffer can't fill up.  If you "fix" an error by increasing the buffer, it is very likely not a real fix.