03-08-2012 02:24 AM
Hi all,
I am a new user of Labwindows/CVI
And I am trying to do an HMI of a 4 channel scope. But I cannot display the 4 different plots on the same graph with different scales like when you change the Volts/division bouton (I succeeded to display the four plots with the same scale)
I find this method for Labview http://digital.ni.com/public.nsf/allkb/049C7E362BE4270A8625756E005CC46F
but not for CVI and it seems to be possible to do it for 2 scales but not 4...
Thank you for your help
03-08-2012 02:41 AM
Hi,
It is possible but not with four different Y axes because the graph control natively supports a maximum of only two different X and two different Y axes. (I any case, the scope also shows just one Y scale, right?)
So what you can do is use the PlotWaveform function for plotting your data; this function provides the two parameters yGain and yOffset which you can use to individually scale your plots.
03-08-2012 03:04 AM
Thank you for your help
Wolfgang a écrit :
In any case, the scope also shows just one Y scale, right?
Yes and No. There is only one scale, but you can change the voltage/division (Channel1 with 5V/div, Channel2 with 10mV/div, etc...) and it is what I'm trying to do. And on CVI, if I don't use multiple scale, there is no way to compare such different signal. It's hard for me to explain it clearly...
Wolfgang a écrit :
So what you can do is use the PlotWaveform function for plotting your data; this function provides the two parameters yGain and yOffset which you can use to individually scale your plots.
I already did this possibility, but I have a big loss of precision. Maybe I did it wrong
I will try again
Any others suggestions?
PS : sorry for my bad English
03-08-2012 03:15 AM
Hi,
yGain should be the equivalent for your Voltage/division setting.
If you prefer 4 Y axes this is possible with some extra effort (but as said I am not sure that you need this extra effort: It should be possible to have four numeric controls setting the individual Ygains of your waveforms).
Concerning multiple axes, you could either have two (or more) graphs on top of each other (the upper graphs have to be transparent, of course), so that each plot/waveform has its own graph with its own Y scale.
Another example is shown in this contribution from Roberto: http://forums.ni.com/t5/LabWindows-CVI/multiple-axes/m-p/31872/highlight/true#M2845
03-08-2012 03:18 AM
Thank you very much
I will take a look on it
03-08-2012 03:20 AM
Hello fredob,
I have published this sample project some time ago that addresses the need for a multi-axis graph control. As you will see, I am using a set of controls to obtain final result, and you can extend this method to as much scales as you want. It is not a native control like the LabVIEW one and it implies some coding on your side to use but it can be a feasible solution.
I have developed it to be used as a post-processing visualization tool, though: I don't know how it will perform in a dynamic environment like your scope interface. Nevertheless it may be a good starting point for you to test.