Read DAQmx: timeout too long

Question

Hello,
The DAQmx Read VI does not seem to take the timeout I set into account: when the connection with my cDAQ 9181 is lost, I would like the Read VI try only once to read the data and quicly return an error instead of waiting for 10+ seconds.
The attached screenshot summarizes the problem: I let the while loop run for a while normally before to unplug the ethernet cable from the cDAQ to simulate a network failure. As you can see, it took more than 18 seconds for the Read VI to return an error although I set the timeout to 1 second.
I am obviously misunderstanding something, but what?
The module is a NI-9206
Thank you!
LabVIEW 2013 SP1
Windows 7 64bit
Windows Server 2012 64 bit
Windows 8.1 32 bit
Attachments:
BD+FP.png ‏86 KB

Answer 1

John_P1 wrote:
ben64 wrote:
The 1000 ms wait is useless and may occur before the DAQmx Read vi adding an extra secondif so. The DAQmx Read.vi will wait until data is received or 10 sec and then generate an error.
It's true the 1000 ms wait is useless, but I wouldn't expect it to add to the loop time since it is executing in parallel with the read
John, I would have agreed with you, but following Ben's suggestion, I removed the Wait 1000 ms and the last iteration of the while loop indeed took about 10s to complete. I don't understand that at all. If somebody could explain...
Now if I use a timeout equal to the inverse of the rate, the VI timesout as expected (see attached screenshot). Thanks guys, I wish I could mark two posts as solution.
LabVIEW 2013 SP1
Windows 7 64bit
Windows Server 2012 64 bit
Windows 8.1 32 bit
Attachments:
Screenshot.png ‏48 KB