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Keysight U2356A inexplicable timeout fixed by probe in subvi

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I am working with a Keysight U2356A and am using the VISA serial library from NI in LV2017. After some undefined period of time, I get the error -1073807339 from Agilent U2300 Series.lvlib:Wait (AI Continuous Acquisition).vi. According to NI this is a timeout error. However, this error gets thrown before the timeout duration is even close to being fulfilled. With a timeout of 10s, the acquisition loop exits after only 1ms when the error is thrown. I need to reset the device and run/exit the VI once to reset the DAQ references; then I can run the VI properly again (). I am not entirely sure, but I get the feeling that this error takes longer to occur in the more basic included example than the current test program, but it happens nevertheless. By chance I have found out that if I place a probe in Agilent U2300 Series.lvlib:Wait (AI Continuous Acquisition).vi, this error does not seem to happen at all. I am really not sure why this might be the case. Might anyone have an idea?


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So I was working on this some more today. I forget what exactly I changed, but eventually I started seeing viWaitOnTimeout (#BFFF0015) errors in the NI I/O Trace tool similar to this thread. Based on this I switched all of the serial calls in Agilent U2300 Series.lvlib to synchronous mode and the issue appears to be resolved. I did this VI by VI and the change in Agilent U2300 Series.lvlib:Wait (AI Continuous Acquisition).vi did not fix the issue, but the calls in Agilent U2300 Series.lvlib:Fetch AI seem to have fixed it. Only time will tell if it crashes again, but so far it hasn't since I made the change. I still have no idea 1) why the timeout was happening so rapidly apparently and 2) why the probe I set might have prevented the issue. 

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So it seems that that was not the solution. I am not sure about if the probes actually helped or not, but the situation persisted despite switching to synchronous VISA calls. However, I think we may have narrowed down the culprit. I am running this DAQ on a laptop. Based on some other threads I found, I unplugged the laptop. With that, the acquisition ran for 40 minutes no problem. Within 10 seconds of plugging the laptop power block in, the acquisition crashed with the above timeout error.


Does anyone have experience with this? A colleague thinks connected the ground levels of the laptop charger and the DAQ supply would eliminate the issue. I have also seen USB opto-isolator modules as a potential solution. I'm not really sure about any of the above and would love some feedback from people with more wisdom about such things.

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Accepted by topic author ConnerP

A USB opto-isolator turned out to be the solution.

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