How can I select multiple channels and plot it in the same graph?

[Gustave]

I there,

I begin in LabVIEW and I try to select multiple channels and plot it in the same graph.  I know the signals are not take at the same time by the DAQ.  I try to select one channel at a time in a shift register but there is only one channel in the graph  because I don't know how to get the 3 waveformes.   You have an exemple of this section of my code in attachment.

I use LabVIEW 8.6 base edition.

Thanks a lot

Gustave

[mallyaprs]

hi there,

 From what i have understood , u need to collect data from three channels and display them seperately on the same chart.

Instead of acquiring these channels seperately in three tasks ,acquire them in a single task and display the same. Look at the attached VI.

For any further help do let me know

[Gustave]

I Mallyaprs,

Thank you for your answer.

For my application, I need to select channels seperately because I would like to be able to change the channel during the test.  I don't want to reselect them when I need to change one.  Is it possible?  

Thanks a lot.

[devchander]

Hi Gustave,

Why not you scan all the channels in the same task and then, index out those channels that you want to display/use

Regards,

Dev

Message Edited by devchander on 09-17-2008 01:58 AM

[Gustave]

Hi,

thanks for your answer.  I review my design but I don't know how to index all channels in my task to select them to make my graph.  I want to read channels in my task not channels available on my environment.

Thanks a lot again!

Gustave 

[dansch]

Hi Gustave,

I am still slightly unsure of your end goal for your application, but it sounds like you are just trying to only graph certain channels from your measurement task rather than all of them at once. If this is the case, the solution is simply to index the array being returned by the DAQmx Read VI, as devchander mentioned. Each element of the array corresponds to a certain channel (since you are just reading a single sample at a time), and so by indexing certain elements of the array to graph, you can just view those channels. Since the DAQmx Read VI is in the loop, you can select which element(s) of the array you wish to index out each time. Hope this helps,

[Gustave]

Thank you for your help everybody, this section is good!!  🙂

Gustave