Allocating 6009 input channels

[martinlz]

Hi

I'm using a 6009 to acquire signals from 3 sensors, get the Power Spectra and display the results; see attached block diagram . What I want to do is to allocate the analogue inputs to specific plots, however the allocation of the channels to plots is not always as I expect. If I run the vi from the start/stop buttons on the menu bar then the plots are allocated consistantly ( see 'white trace a0'). However If I teminate the vi using the save & close control, the next time I run the vi from the start button the colours have swapped around- see 'red trace a0'.  Stopping the vi and restarting from the menu buttons restores the order. I've place a probe control on the output of the DAQ Assistant and it seems almost as if a buffer is not being reset as the order of the channels changes. The 3 input channels a0-a2 have been set up  for : 10v continuous, 4500 samples @ 4.5Khz.

This must be such a fundamental requirement that I think that I must be miising something obvious......Any ideas gratefully received!!

P.S. Sorry if this post is a bit verbose!!

[K_Bull]

Hi,
I cannot see any differences in the two pictures you posted, can you elaborate please.
Thanks,

[martinlz]

Hi,

Whoops! Sorry I posted the same picture!

I have attached two more screen shots, to show the problem. I'm feeding the output from a signal generator to the a0 channel, and channels a1 & a2 are shorted to earth. I expect that the trace displaying the signal will always be tthe same colour. However, as I mentioned in my post, it seems as if a buffer is not being reset and so the data for the channels is not in the same position as observed by a probe placed on the output of the DAQ Assistant.

I have also tried to use the low level task option rather than the express vi but I get the same result, see attached screen shot.

I'm using LabView 8.5 Developer Suite.

Hope that this clarifies the problem.

Thanks

[K_Bull]

Hi,
I have tried to replicate the issue. I supplied a 100 Hz signal to AI0 and grounded the other two inputs > ran your VI, I seem to get the same response all the time. I cannot see the change in colour of the representation as you describe.
Is there anything I am missing? Also, which buffer are you referring to?
Cheers,

[martinlz]

Hi,

Thanks for your efforts. The buffer I'm alluding  to is the array that is shown when  the probe is attached to the outout of the  DAQ Assistant express vi. I've noticed that when I have had error messages on other applications e.g. 200278 a ref is made to 'specify a position and offset which selects a sample.......' , hence I thought there might be a low level type of comand,rather like a property node, but for DAQmx which might explicitly set the position in the array, which is why I sent the DAQmx screen shot.  I've attached a couple of screen shots and a word document that has some shots of the probe outputs showing how the data has swapped position.

I don't think that you are missing anything. As I say, I get consistant results using the start & stop menu buttons and only experience this problem when I've used the 'Save & Close' button to exit the vi and then re-run from the menu start button, presumably with the vi still in memory. The spooky thing is that the behaviour that I observe is very repeatable!  I'll try this on another machine and see if I get the same result. Meanwhile if you have any thoughts or suggestions........

Thanks again