Labview performance suffering with analog input

[nick525]

Hello,

I am using a PCI-6036E and a cDAQ-9172 with LabView 8.0. I have created a VI that systematically writes four different digital outputs, three to the PCI-6036E and one to the cDAQ-9172.

Just recently I added a thermocouple to the mix, using an analog input on the PCI-6036E to monitor temperature. Since doing so, I have noticed that the entire VI runs extremely slowly.

Before installing the thermocouple, the VI slowed down a bit if left to run continuously (for days at a time). Now, however, the VI slows down a great deal if left to run for more than a few minutes. It is so bad that the "Elapsed Time" display will not properly display the elapsed time.

Because this application will be run for days, even weeks at a time without being stopped, this gradual decrease in performance is a huge problem. The application needs to run very accurately and precisely. I have attached my VI below. Is there any way to fix this issue? Any help is greatly appreciated, as I am new to LabView.

Thanks,
Nick

[nick525]

Sorry, forgot to attach my VI. Here it is.

[TCPlomp]

I didn't look at the code (yet), but do you have a slow analog samplerate?

Look here
And here (a KB aticle)

Ton

[Matthew_Kelton]

Your thermocouple read takes 100ms (1kHz/100 samples).  Because a calculation based in the result is wired into your case structure, none of the other code can execute until the thermocouple reading is taken.

[nick525]

How would I go about changing the code such that the thermocouple reading and the remainder of the case structure function independently?

[nick525]

I am not sure if I have a slow analog sample rate. I took a look at the resources you posted, and will try setting the Data Transfer Request Condition to fix my problem.

[MikeS81]

Hi nick525,

you can create another while loop parallel to your existing one and read the temperature value there.

Mike

[nick525]

I was a bit curious, so I removed the temperature component of my VI completely. After running for a few minutes, my VI still becomes rather lethargic. The elapsed time display seems to be behind a bit, and the start/stop/pause features all take about 15 seconds after being clicked to respond. Is there a way that I can fix this? Obviously the analog input had some effect on performance, but even without it there is also an issue I cannot solve.

[MikeS81]

Hi nick525,

every time you write one of your values you create a new task. Why? I think a much better way is to create the task ones at the beginning and use everytime the same.

Mike

[nick525]

How would I go about doing this, by creating a shift register and storing the values?