DAQ Assistant

[freserf]

I am using LabVIEW 2017 along with the USB-6210 to collect a voltage signal and encoder counts.  I am using the encoder counter(PFI0) as the trigger to collect 8000 voltage signals.  The signals are being collected and analyzed properly so I know that the counter is working or I wouldn't have any data, but for some reason I cannot understand yet, the encoder signal count is not being updated and passed through my VI.  I use the same setup for several different VI's ... basically identical and those work without issue.  Has anyone experienced this erratic behavior?

[GerdW]

Hi freserf,

the encoder signal count is not being updated and passed through my VI. I use the same setup for several different VI's ... Has anyone experienced this erratic behavior?

Why and how should we have experienced the same problem with your VI?

Maybe you should attach your VI so we can examine it?

Some people might even consider using the DAQ Assistent (or other ExpressVIs) as a generic problem…

[freserf]

Well ... technically I cannot share the VI due to corporate policies.  I understand the logic of having something to look at in helping with troubleshooting.  I deal with troubleshooting many different systems on a daily basis and when faced with the unusual, odd problem, I ask first if someone else has experienced this issue.  For example, we have a system that uses LabVIEW designed by an outside Engineering firm that I do not have access to so it makes it more challenging to troubleshoot.  So here is a description of what is happening.  I am using two DAQ Assistants to gather data from a USB-6210.  One is from a laser to voltage signal +5 to -5 volts that is triggered by an encoder setup as a Linear Position using X1 decoding collecting A and B channels.  Samples are 8000, and rate is 2000hz.  When checking the signals using NI-MAX, I can see the counts no problem.  The laser is setup for voltage as I mentioned and is triggered to collect 1 sample for each encoder PFI0 rising.  I need 8000 samples at 2000hz.

The encoder signals are passed to a Statistics Express VI looking for the last value and total samples.  Here is where I seem to be losing something.  The last value reported is "0", but the total samples equals 8000.  I use the last value to indicate encoder counts and the total samples as a test before any of the laser data is analyzed.  This is a simple AND ... I have to have 8000 samples and no errors before any analysis is performed.

The problem is that even though it appears to be working and analyzing the signal, there is no encoder data being passed to the analysis case structure.  This data is coming from the DAQ Assistant.

How can it be working, but not working?  In comparing to other VI's that we use for reading, they are identical.  If the DAQ Assistant and other Express VI's are programmed time bombs ... that would be good to know so I can avoid using them.

Thanks for the response and have a great day.

[GerdW]

Hi freserf,

technically I cannot share the VI due to corporate policies.

You cannot even create an example VI to explain/recreate your problem?

The encoder signals are passed to a Statistics Express VI

Oh, one more ExpressVI…

The problem is that even though it appears to be working and analyzing the signal, there is no encoder data being passed to the analysis case structure.

Did you do some debugging? Which data is writed from one ExpressVI to the next?

To debug: which data is coming from DAQAssistent? Which data is going into StatisticsExpressVI? Which data is coming out from StatisticsExpressVI?

If the DAQ Assistant and other Express VI's are programmed time bombs ... that would be good to know so I can avoid using them.

I guess you get my disapproval of ExpressVIs for production VIs…

[freserf · Accepted solution]

Thanks for the response,

No I do not have time to create an example ...

Yes, this VI uses Express VI's ... why have them if they are a problem ...

Yes, performed simple analysis with no major warnings ...

I do not need your approval or disapproval ...

I do appreciate your offer of help ... 

Have a great day.