AI config.vi

[DarkMarc86]

Hi guys, I am new to LabVIEW and I am trying to understand a program that a work collegue of mine has written. Basically the program just acquires data at 500Hz sampling rate from accelerometers. Anyway, one of the first functions he has used is called AI config.vi and for the "channels(0)" input there is what looks like a single element array on the front pannel which says 0:3 and there are active 15 channels in the program. I am trying to extend the program to 25 channels. If type in 0:5 in the box in teh front pannel I get 24 channels that I can read from, and 0:6 gives me 27 channels, so it seems that every time I increase the number by 1 it gives me 3 extra channels for some reason. Is tehre any way to get exactly 25 channels, and does anyone know why this is happening?

Alternatively, if someone could tell me where I can find a good explanation of this function, that would be handy as well. Thanks in advance.

[MattBradley]

Well, AI config.vi sounds like Analog Input configuration.  Beyond that.... hard to tell.  Any chance you could post the whole VI or at least a screenshot of it?  (AI Config.vi, that is).  Also, what card are you using to do the data acquistion?

-Matt

[DarkMarc86]

I'm using a National Instruments DAQCard-6036E card, although it's not connected to anything at the moment; it's just sitting in the laptop. I'l post a picture of the VI tomorrow, but I would have thought that you would be able to access it yourself in LabVIEW?

[Dennis_Knutson]

You really need to post the actual VI and not an image. Need to see how your channel control is filled in. My guess is that the channel array is actually multiple elements and that 0:3 is only the first element. If you only have a single element with 0:3 listed, then there are only 4 channels being acquired.

[DarkMarc86]

Ok I have attached AI config.VI. Althought I still don't understand why you guys don't have access to it throught your own copies of LabVIEW.

[Dennis_Knutson]

We do have access to it and but as I explained, we don't have access to the code that you are working on (where the function is being called) and that you believe it acquiring more channels than specified. If you want an explanation of that, you need to post that code. And as I've already said, if the only thing that is in a channel list is 0:3, you will acquire data from exactly 4 channels - no more and no less.

[DarkMarc86]

Because the program was done at work i'm not sure if I have permission to post the entire thing. However I can probably post a screenshot of the section of code which uses the VI. Do you want the relevant bit of front pannel as well?

[Dennis_Knutson]

I don't want a screenshot at all. Since the input is an array, an image is not going to show what is defined in other elements of the array. What I suspect is that you see channels 0:3 in element 0 but you are not looking at the other elements. For example, element 1 of the array might list channels 4:14 and that is why you are acquiring 15 channels.