basic input problem

[emer]

Hi,
I'm having trouble reading in basic voltage inpus. The error 50103 keeps coming up and I can't find a way to amend it. Any Suggestions would be greatly appreciated.

[JoeSavage]

You've got two AI tasks configured to run simultaneously on the same device. You can't do that, because the device has only one AI timing engine. Instead, create a single task that contains all of the channels you want to read.

Joe

[emer]

Hi,
Thank you for your advice.
Is this what I have to do? I.e. use just the one DAQ to read in multiple channels?
I then have to perform opreations on these signals. How do I separate the signals so that for example I can mulitply signal 1 by signal 2? I have been looking for a VI that will take in the dynamic data and convert it into my separate channels.

[ryanw]

Hi Emer,

Yes, this is what you need. What you need to do now is plit the signal that is output from your DAQ assisstant, (the deep blue indicates a dynamic data). The splitting can be done using the merge signals node's, found on the functions pallete>>signal manipulation. See the adaption that I've made to your example.

As you're learning with LV, I suggest making good use of the tutorials and examples in the developer zone on our web-site: http://zone.ni.com/devzone/devzone.nsf/webcategories/4d58b1b80ec41ef70625683f006e1d6d

You can also search the examples that ship with LV by selecting, (from the vi menu bar): help>>find examples, then either brouse the topics, or perform a search on a key word. For example, under continuous acquisition search, I found the second example that I've attatched. This is a continuous acquisition set-up using the DAQmx vi's. When you get more experienced with LV, you will probably transition from using the DAQ assisstant to using these sub-vi's as they allow the user more control, (eg. setting sample rate's etc..). Brouse through some of these example's as they will help you learn.

Hope this helps,

Ryan.

[ryanw]

Here's the second example,

Ryan.

[emer]

i need to sample 4 input signals as fast as possible, process the data and generate 2 outputs.

the problems i am encountering are:

I had a look at the example you sent me but I don't fully understand it and as I have time constraints I need finish my Labview project as soon as possible.

I have set up the input DAQ Assistant to samples to read = 1, continuous and frequency 1000Hz.
Is this the fastest rate to input data for my system?


I am unsure as to how the outputs should be configured. Is the method I'm using correct? or is there a better approach to output the data?

To allow the data be manipulated by a formula, the data is passing through a CDD (CONVERT TO DYNAMIC DATA) and the to an eval parsed formula string. Is the formula being performed on all my necessary input samples using this method?

Lastly, logging the data: When I check the input data log, with samples to read = 100 the timing column corresponds to the amount of time I let the system run for but when I change the DAQ Assistant to samples to read = 1, the timing no longer corresponds to rel time. e.g. if I let it run for 10 seconds the timing shows:0.001, 0.002 etc. but then it goes from 0.34 to 10.396???

Also the timing for the output log does not show any times corresponding to outputs.

Any help would be great,
Thanks

http://forums.ni.com/attachments/ni/170/108778/1/code.vi

[George M.]

Hi,

I see that you had some questions that have not been answered a while ago, but it also sounded like you were under time constraints. Were you able to look over the material posted in the previous posts to figure out what is going on, or are you still having trouble. If you are no longer concerned about this, please disregard this post.

George