Using multiple channels in a program

[Ryan23]

I have a strain gage program that was written using LabVIEW 5.1.  The program uses 15 virtual channels.  Recently, we purchased a new computer and installed LabVIEW 8.2.1 on this computer and also installed Traditional NI-DAQ drivers 7.4.1.  The virtual channels were manually entered into MAX to reflect the virtual channels from the old system.  All the VI's that were created work fine when only one virtual channel is used/referenced.  For all the programs that use/reference multiple channels, though, the readings are all over the map and bounce around (having the cables connected to a strain gage has no influence on the displayed value at all).  If we remove all but one of the channels and have all the indexing arrays have "0" for the input element everything works fine and the value we want from the strain gage is indicated on the graph and indicators on the front panel.  By fine I mean the program works but shows the same valve in all 15 indicators.

Is there a different way to note the virtual channels in LabVIEW 8.2.1?  LabVIEW 5.1 used commas to separate one channel from the next for example.  Is this different in LabView 8.2.1? 

Ryan Williams   

[Abhinav T]

Hi Ryan,

Thankyou for posting to the National Instruments Discussion Forums.

The Traditional NI-DAQ virtual channels have not changed since LabVIEW 5.1.

What Traditional NI-DAQ VI are you using to read the values from the channels?

[Ryan23]

Thanks Abhinav,

I have attached two screen shots as an example of the programs we use.  Like I said in this setup, for some reason, we get no readings of value on the front panel when running the program.  Whether the cables are connected or not makes no difference.  Yet if we delete all but one channel inputs (mvolts1, mvolts2, etc.) going into "AI Config" and change all the constants attached to the arrays (whose inputs come from "AI Read") to "0" the program works fine.   

Ryan

[AnalogKid2DigitalMan]

Ryan:

Your screenshots failed to attach

[Abhinav T]

Ryan,

I did not see any attachments to your post. Can you please repost? Also what data acquisition device are you using?

[Ryan23]

Sorry.  I it was a bmp file.  I resaved it as a jpg.  Hopefully this works. 

I am using a DAQCard-6036E for Data Acquisition.   

[Abhinav T]

Ryan,

Few suggestions:

• Try entering each channel as a seperate element of the input array, this is another way to specify multiple input cahnnels 
• Try using the physical channel number (0,1,2) and see if you get a better voltage reading (it will not be scaled correctly but it will give use some idea of what is going on)
• Replace the Traditional DAQ code with a DAQ Assistant. Here is a tutorial you can follow to read data from an analog input channel using the DAQ Assistant Express VI

I especially recommend the last suggestion, changing the code to NI-DAQmx (using the DAQ Assistant). I understand that you have been using this code for sometime however the newest DAQ driver is much easier to use and gives you the flexibility to perform much more than the Traditional DAQ driver (what you are using).