continuously acquire two different signal at the same time

[garfield]

I am student working on project that uses LabView to implement a digital Proportional Derviative controller.

I need to acquire two signals from a system. They are both continuous and must be read at the same time so that the VI can calculate the exact error. I'm not able to acquire both signals on the same graph and also the voltage values are required for calculation. With my present VI, it displays the same waveform for both channels.

I am using Traditional NI-DAQ, AT-MIO-16E-10 and LabView 7.1.

I'm very new to LabView and appreciate any help I can get to solve this problem.  

Message Edited by garfield on 12-16-2005 03:58 PM

[devchander]

Hi,

Search in  lab view examples and use any continous Voltage acq programs

this attached VI( taken from above mentioned examples) will do continous acq from any number of channels on a DAQ card

Regards

Dev

[devchander]

Sorry forgot to tell you to read documentation  at menu->  File-> VI properties-> documentation , to get an idea as to how this VI works

Do tell if you have any doubts.

Regards

[garfield]

Hi sir,

appreciate your help very much. The attached vi works fine. But I need to use the voltage values for data processing. I should use a 1D waveform array to display that right. Another thing is that how can I seperate the two signal values?

thanks & regards

[devchander]

Hi Garfield,

This is what you can do

1. To get individual voltage's data from an 2 D arry, just index out the relevant column to get the corresponding channel's data ( look at attached Cont Acq& wavefrom_voltage.VI)

2. To get waveform display, do as shown in attached Cont Acq& wavefrom_waveform.VI.

Here data from AI read is read as 1D wavefrom array, each channel's waveform cluster is indexed and the voltage data is unbundled out of it.

Hope this helps

Regards

Dev

[garfield]

Hi Sir,

thanks again for your help. The attached VIs made it a lot easier to understand.

regards

(Merry Christmas & a Happy New Year to you):smileyvery-happy:

Message Edited by garfield on 12-20-2005 10:26 AM

[devchander]

Hi,

Glad to be of help

Merry christmas and happy new year to you too!

regards

Dev

[JohnGW]

Hello.... I am making the move from VXI to DAC cards on some of my test systems. I am looking for an example to continuously acquire 2 channels of input like the example above (Cont Acq&Chart (buffered).llb) but using the new DAQmx vi's.

My sample rate needed is 200HZ per channel and I would like to get scan updates to graph on the screen at least 10 times a second (first channel only).  I will be using the second channel to stop the data acquisition (when the voltage > 3 volts).

I have setup a task in the Data Neighborhood called 'test1' that includes global for Channels 0 & 1. These are setup as RSE inputs.

The example listed above works but I figure that it might be best to start off using DAQmx but I don't see any of the DAQmx examples that comes with Labview 7 that compares to the example listed here.

Any help?

Thanks

John

[devchander]

Could you plz tell which DAQ card you plan to use??

[JohnGW]

I am working with the PCI-6052E right now but will be switching to the PCI-6229 when it gets here.

Thanks

John