How to program the output data of a DAQ assistant?

[sunbird]

I am new to LabVIEW. I am acquiring a signal using DAQ assistant. After I acquire that signal, how can I program it? For example, if I want to multiply the signal with 2 or I want to connect it to a formula node, it can not be wired because the data type does not match. Besides, the signal I want to get is discrete samples.  I will really appreciate if anyone can give me anyhelp. Thanks a lot!

[devchander]

You can perform arithmetic operations(  in your Functions palette) on a signal that is read by using a DAQ assistant ( Dynamic Data type)!

Additionally, you can convert the Dynamic Data type to any of the selectable forms ( in your case must be a 1D array) by using Convert from Dynamic Data function found in Functions palette>>signal manipulation

Look at attached pic

[bburress]

Hey sunbird,
    devchander hit the nail on the head with his response.  The output from a DAQ assistant is dynamic data.  In order to use this for anything other than displaying in a graph or chart, you need to convert the dynamic data to another type, depending on how you setup the DAQ Assistant.  Once the data is converted, you can manipulate it just as you would any other data in LabVIEW.

[sunbird]

Thank you so much! Both of you helps a lot!

However, I have another question. What I want is to acquire a signal discretely, say I have a thermistor, and I want to acquire the voltage and the temperature(transform to a voltage also), and then pause the program, then change the temperature, and then let the program go on to get the pair of signal, and so for. I had done this by a even structure. However, I want to display the signal in a graph. My graph can only have the recent signal but erase the previous ones. Is there any method I can keep previous dots to get the curve of voltage vs. temperature? I tried to use shift register but failed. Attach please see the diagram. Thank you!!

[devchander]

Sorry could not open your vi as i have labVIEW 7.1 installed on my system

But to do you have explained, why not ues a chart instead of a graph???? (here you will not need shift registers)

Also, use a local variable of that chart in your other event case and keep wriiting to the existing chart

Hope this helps

Regards,

Dev

Message Edited by devchander on 10-11-2006 11:08 PM

[sunbird]

Hi Dev,

Thanks a lot for your help! However, it seems chart  can not plot the relationship between two signals. The input of x axis of chart should always be time, isn't it?

Thanks,

[devchander]

Yes the x axis to teh chart will always be either in terms of Absolute/ relative time or number of samples

Could you please post a picture of your block diagram ( with all events) ??

I could take a look at that and suggest better

Or probably in teh meantime, someone else will take a look at your posted vi and give a good suggestion.

Regards

Dev

[bburress]

Hey sunbird,
    Check out this screenshot.  It shows how to use the shift registers to build up an array of X and Y values to be used in the chart.  Let me know if it helps out.  Thanks!!