Plotting data from two instruments at different rates

[Foronda]

Hi,

I have a VI that reads temperature from a multimeter using VISA and acquires image from a IR camera via IMAQ. Each acquisition process takes place in an independent while loop; each with its own frequency. From the IR image I get a pixel value which is converted to temperature.

My problem comes when I try to plot both signals (temperature from the multimeter and from the pixel in the IR image)in one chart. Just merging signals doesn´t work. I have embedded the multimeter section in the "while" loop corresponding to the image acquisition. This works, but speed is limited by the multimeter, which is very slow (approx. 1.5 Hz)

I would like something like this: if I get 50 images and 1 multimeter reading
in a certain period of time, set up some kind of buffer so that the 50 values from the camera are plotted as well as the one from the multimeter reading repeated 50 times. I´ve tried resampling but to no result.

Sorry if something is not quite clear, please tell me if I should be more specific. Thanks in advance for your help

Alberto Foronda

[Ben]

Try putting the data from each souce into a waveform (see the waveform pallete). Make sure you write the t0 of the waveform. Do this for each reading, and then build an array of these waveforms and then present this to your chart.

THe Chart will use the t0 of your vaeform to plot your data. It will not matter that the time are different, that chart will figure that part out. If you have data from your camera but no new reading from your multimeter, just make sure the waveform for the multimeter has an empty "Y" array. This will plot the camera data but it will leave the multimeter trace alone.

Trying to help,

Ben

[Foronda]

First of all, thanks for your reply. However, I´ve tried to implement what you suggested and realized the problem lies deeper, since I can´t get data out of the while loops until they stop (and then I can´t measure!). I´m posting a very simplified VI which is essentially identical to the one I´m working on, so you can get a better idea of the situation. Any suggestion would be much appreciated.

Thanks again for your help

Alberto Foronda

[Ben]

Sorry but I have not installed LV 7.1 yet.

This is a seperate question that I suggest you post as a new question in order to get full exposure to all of the Enthusiasts.

In the meanwhile, please take a look at this thread.

http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RPAGEID=137&HOID=50650000000500000015A30100&HTHREAD=000107285000107320000107385000107415000107428000107429000107566000107578&UCATEGORY_0=_49_%24_6_&UCATEGORY_S=0

In that thread some of our big guns discuss methods of moving data between parallel processes.

Ben

[YonA]

Hi!, Have a look to the VI attached below. You should use a Graph instead of a Chart.