multi channel daq read

[delpitik]

I have a problem with the daq read in labview 7.

When I have used labview 6 and I has to read 2 groups of channels at different frequency, I has made one program with 2 while cycles and in one I read the first group at f=x, and in the other the second at f=y and all run perfectly.

The same program in LW 7 run but at the first acquisition stop and write one error.

I have the same error if I read AI in one part of program and TC in other part.

The program run correctly only if I put all channels to acquire in the same frame and at the same frequency and then I move them with local variable.

You have the same problem or not?

Thanks

[devchander]

Were you performing single point AI read ( inside a while loop) in LabVIEW 6??

Or were you performing continous AI read?

[delpitik]

I perform AI in while loop every 100 ms

[devchander]

I am assuming that you are using a multifunction DAQ card

Since all your AI channels share a single ADC, as AI read in one loop has reserved your ADC and the other loop is trying to access it at the same instant, you are getting this error

Infact i am surprised how come this error did not show up in LabVIEW 6 itself??

Which DAQ card are you using??

And if you want to continue as per your old method ( which is probably by performing single point AI read in two loops), I suggest you perform some software synchronization between the two loops

Use semaphores and thus ensure that the two loops do not conflict for the same device (and hence you will avoid the error)

Look at this link or look at semaphores examples shipped with LabVIEW

Again, there are a lot more things that I would suggest.

Get to using DAQmx device drivers, if your device supports it ( I suspect you are using Traditional DAQ functions)

Perform a hardware timed continous acquisition in a single loop and then seperate/decimate out the AI and TC data

[Christian Mergl]

I'm fully agree with devchander.

It would be interesting to know the error number (must be -50103) and the hardware you are currently using and the one you used with LV 6.x.....if it was another one.

Message Edited by Christian_M on 01-08-2008 09:05 AM