Splitting up plots on XY Graphs depending on zero crossing

Hi,
I posted this question earlier and thought I got a solution. Please read the old thread: http://forums.ni.com/ni/board/message?message.uid=1098899#U1098899
Basically, my problem now is that the way its being done now, whenever it crosses the zero axis with a negative slope, it temporarily creates another plot and as soon as it crosses it with a positive slope, it merges those 2 graphs together. So somewhere between the slope going from -'ve to +'ve and crossing the zero, I have an extra plot, and it distorts the colors of my plots, which seems like a bug to the user and may confuse them. I have attached a VI below where you can see this behavior in the 2D array indicator.
Attachments:
XY Example VI.vi ‏18 KB

I don't know what your intentions are with this VI, or what you mean by "temporarily creates another plot".
You've got a lot of array manipulation going on inside those loops. You are just going to have to sit down, figure out how those loops are currently working, and how to change them if they aren't doing what you want.

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Go to Solution.
Attachments:
Test_1.vi ‏13 KB

Here's a more scalable solution, useful if you have one x and many y columns.
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Good Day,
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Attachments:
hysteresis.vi ‏176 KB

As it turns out, the issue was that I was not collecting enough samples at a high enough sample rate from the DAQ. This is why it worked with "Generate Signals" and did not work with the DAQ Assistant. Because there were not enough samples, the apparent zero crossing was occuring either too early or too late, leading to an incorrect value. Therefore, the best solution when it comes to finding zero crossings is make sure your # of samples, and sample rate are high enough to get an accurate measurement.
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How to measure time difference between zero crossing of a sine wave and rise time of a pulse on a same graph?

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Message Edited by awais.h on 03-30-2010 11:20 PM
Message Edited by awais.h on 03-30-2010 11:21 PM
Solved!
Go to Solution.

Hi
Thanks for the code but I'm afraid it won't work. Like you said the probability of choosing a value that is on both graphs may not happen. This is something that I would like the code to do automatically.
But I did use the previous code posted and made some modifications to it and it seems to work perfectly. Now the next thing is to be able to get just that one value that tells you the first time difference.
Here is what I get using that code.
As you can see from the t Values. I only need the one that is highlighted. If there is a way to filter out the rest it would be great.
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Here is the the code modified.
As you can see, it wasn't that big of a modification and it still is your code.
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FinalShockSpeed.vi ‏55 KB

How to make sure plots in xy graph are present?

Hi community,
since updating to LabVIEW 2014 this week I have an issue with code that worked previously (or didn't but the problem was unnoticable).
As shown in the example llb I created to showcase the issue, I'm filling xy graphs with quiete some data and then programatically colour the plots.
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Solved!
Go to Solution.
Attachments:
colour.llb ‏194 KB

Florian,
i cannot run your example as it requires some VIs from a LAVA-library (which i dont have installed).
Nevertheless, there are some questions i am stumbling about:
1. Why do you use a local variable rather the terminal to pass all plots to the indicator?
2. If you place a wait function in the sequence frame which waits longer than the expected time for passing the data, does the error still occur?
3. Do you run into the error if you enable panel updates before coloring the plots in order to slow coloring down?
I can imagine that you have a race condition against the UI thread. The local variable (just like the terminal) has a buffer where the data is copied to. The UI thread will retrieve the data as soon as it is ready. I would expect the coloring to require the data be present in the UI thread already (in order to "acknowledge" the plot). So if, for any reason, the UI thread only cought 98% of all plots when you start recoloring, you race against the transfer of the last 2%.. depending on the UI thread execution speed, you can run into the error or maybe not.
That is the reason why i want you to test for waiting times or slowing down the coloring.
Norbert
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Best way to draw (not plot) on a graph?

Hi -
I need to alter the appearance of a graph somewhat. The user doesn't want any full grid lines, but he does want a small crosshair (like a plus sign) drawn in each of the four quadrants. The CanvasDrawLine() function would be good for this, if it worked on graph objects, but it doesn't. I guess I could use bit files, but...is there an easier/better way?
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Solved!
Go to Solution.

Going on the line of wolfgang suggestion, you could also have two graphs one on top of the other. The lower one can have all fixed elements (scales, axes, crosses and so on), while on the upper one, with transparent background, you can draw / erase your data plots. As long as you keep axes for both graphs with the same scale the system works like a charm, and you don't need to struggle with pixel conversion between the graph and the picture.
Proud to use LW/CVI from 3.1 on.
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Splitting up plots on XY Graphs depending on zero crossing

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