topic Re: Multiple Channels for this program? in LabVIEW

Multiple Channels for this program?

needtolearnfast — Tue, 31 May 2005 14:13:01 GMT

Hi,

I have built the following VI and was wondering if there was any way it could be modified to use multiple (at least 2 but preferably 4-6) channels. I was trying to maybe make the same thing repeated 4 times wo the user could do what is being done now on 4 seperate channels. I'm not sure I can do that the way I'm doing it now as it become very slow. Thanks for any suggestions.

Re: Multiple Channels for this program?

Dr._Imad — Tue, 31 May 2005 14:26:50 GMT

use channel syntax like

0 channel 0
0,1,2 channels 0,1,2
0:2 channels 0 thru 2 (same as above)

0:6 channels 0 thru 6

0:6,7 channels 0 thru6, and 7

0:7 channels 0 thru 7
etc

Re: Multiple Channels for this program?

needtolearnfast — Tue, 31 May 2005 14:31:09 GMT

Thanks for the reply, but I understand that part. I guess I should have been clearer. My question really is once I get those multiple channels read in from AI Read block, is there any way to unbundle the different channels that were input and plot them on seperate graphs? Thanks.

Re: Multiple Channels for this program?

Dr._Imad — Tue, 31 May 2005 14:46:42 GMT

just use the index array function

Index 0 would be data of first channel in the list
Index 1 would be data of second channel in the list
Index 2 would be data of 3rd channel in the list
etc....

Re: Multiple Channels for this program?

needtolearnfast — Tue, 31 May 2005 15:26:32 GMT

Hmm, that doesnt seem to be working as everything that comes out is channel 0 (ie if I have channels 0,1,0 all three will output 0, or if I have 1,1,0 all three will output 0. I reattached the version I have now and have no idea why this is happening. Thanks for any help.

Re: Multiple Channels for this program?

Dr._Imad — Tue, 31 May 2005 15:43:04 GMT

The way you are indexing it is fine.

However, do you get an error message ?
why do you want to scan channels twice (I am not sure if this works, never used it like that before)

<< if I have channels 0,1,0 all three will output 0, or if I have 1,1,0 all three will output 0. >>
instead of using 0,1,0 just use 0,1 or 0:1 and see if it works
Note also for some old daq cards, channels is decending order is not allowed)

Re: Multiple Channels for this program?

needtolearnfast — Tue, 31 May 2005 15:50:07 GMT

I don't get any error messages, but I don't understand what you mean by "scan channels twice" (I'm new to labview, this is my 3rd day using it). Thanks a lot for all your help it is much appreciated.

Re: Multiple Channels for this program?

Joe_H — Tue, 31 May 2005 15:51:26 GMT

You probably cannot go in descending order, use 0:1 to get channels 0 and 1, your indexing is fine and should work.

here are a couple of tips to make your vi run faster.

Put the AI config and AI start outside the loop so that you are not reconfiguring them each time the loop runs, also use the open, write, close file vi's manually. put the open outside the loop at the beginning (like you already have), then write to it during each loop iteration and then put the close outside the loop. this way you are not opening, writing and closing the same file every time the loop iterates.And what he means by scanning channels twice is going from 0 to 1 and back to 0 in the same scan, scans are done going from 0 to however many channels your bord has. if you put in lets say 0:9 the scan will scan channels 0-9 in ascending order then repeat.

just giving some input

Message Edited by jhoskins on 05-31-2005 11:56 AM

Re: Multiple Channels for this program?

Joe_H — Tue, 31 May 2005 15:52:49 GMT

Could you post the version of labview you are using and the DAQ Board model #. This will help us help you.

Re: Multiple Channels for this program?

needtolearnfast — Tue, 31 May 2005 15:57:08 GMT

Here you go:

LabView 7.1

DAQ CARD- 6036E

Thanks.

Re: Multiple Channels for this program?

Joe_H — Tue, 31 May 2005 16:13:09 GMT

Well now we can work, in the examples find a VI called Cont Acq&Graph Voltage to file binary using Daqmx, Modify this as needed or just take a look at it to see how it is done, I prefer using Daqmx it is much simpler (for me).

Re: Multiple Channels for this program?

Dr._Imad — Tue, 31 May 2005 16:23:39 GMT

modified vi attached

Re: Multiple Channels for this program?

Dr._Imad — Tue, 31 May 2005 16:42:25 GMT

However, as Jhoskins suggested, use DaqMx (this is the way to go), and follow the example he pointed to.

Re: Multiple Channels for this program?

kmous — Wed, 18 Jun 2008 18:13:40 GMT

Hi i have my VI and i wanna measure 2 channels one for EMG and one for FORCE ...i connot select both of them ...i can go one by one , how would i select them both at the same time !!!! maybe because i am using Physical channel ?
thank you
Ali

Re: Multiple Channels for this program?

Dennis_Knutson — Wed, 18 Jun 2008 18:38:28 GMT

duplicate post