Plot name errors on mixed signal graph

[scrook]

I'm running into a problem with the mixed signal graph in my project. What is happening is this: the channel name from the DAQ task is not showing up in the plot legend (though it shows up fine under my multi plot cursor) instead of a meaningful name it simply says "Plot1" . Also the very last channel does not show up at all (not even a "PlotX" label) in the legend but it does show up just fine under the multi plot cursor.

To give you an idea of what I mean look at the 'graph.png' attachment I have uploaded. You will notice that in the Cursor Legend the first of the channels is labeled 'AMB' while in the Plot Legend it is 'Plot1'. The very last plot shown in the cursor legend is 'HUMIDITY' which does not exist at all in the plot legend. All other plots are showing up correctly in the plot legend.

I'm not sure if this is a bug in the mixed signal graph vi or if it is a problem with my code. I have attached 2 images (test5.png is the main VI and untitledvi.png is the sub vi that you see in the main image).

[Karunya_R]

Hi,

Which version of LabVIEW are you on?

Are you able to replicate the problem without using a DAQ assistant (i.e. use a simulated signal)?

Is the problem consistently with the last channel or does it drop channels in between as well?

Does the problem still persist when you rename your channel? Or move one of the other channels to the first position?

[scrook]

I'm using Labview 8.6.

I can replicate the problem using simulated signals instead of DAQ assistant.

In both cases (either with DAQ assistant or simulated signals), the names will appear correctly the first time you run the VI. If you clear the graph, however the name of the first channel will always change to 'Plot1' and the very last channel will disappear completely. (Keep in mind that the correct channel names will still be plotted on the graph and shown in the multi plot cursor legend). All other channels except the first and last will display correctly in the legend.

The problem does not go away if you rename or re order the channels. The only ways I've found to fix it is:

1. Delete the mixed signal graph from the block diagram and place a new one down

OR

2. Close all Labview windows and restart Labview and load your VI (This only seems to work if the VI was saved in a state where there were no channels showing in the plot legend) If you have this error condition exists when you start the VI then there is no getting rid of it (short of step 1 above).

I'm curious as to what could be causing this since it doesn't seem to be a problem in the example VI (Though I don't think it made use of Dynamic Data).

[Karunya_R]

Hi,

Can you please send me the VI you tested this with? (A small version would be ideal to identify the problem). 

Have you tested this with LabVIEW 8.5?

Which example VI did you test?

[scrook]

I have attached a small VI which exhibits the problem with 3 different signals. As far as I know I don't have any way of testing with Labview 8.5 since we don't have any licences for it. We had an evaluation version which has since expired and we bought 8.6.

The example VI I tested (which did not exhibit the problem) was Mixed Signal Graph.vi

[Brinoceros]

Hi scrook,

Thanks for posting that small example.  This ceratinly does look like unexpected behavior.  I have played with it a bit with various data types, and I consistently see the behavior you are talking about.  I will most likely submit this to R&D, but I am going to play with it a bit more first.  Have you been able to find a suitable work-around?  You mentioned a couple of methods in your previous post, but those solutions didn't sound too satisfactory.  Please post if you have found a good work-around, or we can try to come up with one.

Regards, 

[scrook]

Brian,

I've not yet come up with a suitable work around. Any help you can give me in coming up with one would be appreciated.

Basically what I am trying to implement with my project is this:

1. A graph that has a multi-plot cursor so that I can see the Y values of all plots at any given time on the X axis

2. I need to be able to view the data on the graph over a course of 24 hours (If charts had the ability to use cursors I would use that but since they don't I am using the collector express VI as a buffer.

I've tried using the waveform graph in the place of the mixed signal graph but when I feed it dynamic data from my DAQ assistant task it adds the Y values of all waveforms together to create a single waveform which is definitely not what I want. Also I'm not sure if you can have a plot legend with a vertical scrollbar with the waveform chart either.

I have another alternative in mind using the mixed signal graph as well. Maybe you can tell me if this is possible. Since the cursor legend does show the correct plot names at all times, the only feature I'd really miss by not using the plot legend is the ability to change the color of a plot on the fly. Would there be a way I could implement this (maybe a dropdown box of all available plots and then a way to change color of that plot)?

Thanks,

Scott

[Brinoceros]

Hi scrook,

First, a note on the Plot Legend behavior you have pointed out.   This was reported to R&D (# 125494) for further investigation.  It looks like unexpected behavior that needs to be addressed.

I believe you should be able to use the Waveform Graph or Chart for what you are trying to do.  Especially since it looks like you may not even have mixed signals to graph.  You can have a vertical scroll bar on the Waveform Graph/Chartlegend.  Right-click the legend, then go to Visible Items >> Vertical Scrollbar.  It also shouldn't be adding the Y values.  Maybe if you can post an example of that we can figure out what is going on.  Try adding a Waveform Graph to the example you already posted and see if that works as you want it to.

[scrook]

Brian,

Can you make a multiplot cursor on a waveform graph? From what I've read here , the multi plot cursor is only a valid mode for the mixed signal graph. For what we are using Labview for, being able to see the Y values of all signals at a given point in time is vital.

As for charts, from what I can tell, they do not support cursors at all. If you know of a way to implement a multi plot cursor to work with either a waveform graph or a chart that would be great but it looks like I am stuck with the mixed signal graph for better or worse.

Is there some way I could implement a custom control (a dropdown which is programatically populated with channel names with a color picker type control) to change the color of a given plot? Since the names of the plots are shown in the cursor legend without error, the ability to change the color of a plot is the only feature I'd really miss by just not using the plot legend.

[Brinoceros]

Your last question, about changing the plot colors, looks like the easiest thing to do.  I've been away from my desk recently and haven't had much time today to make a decent example, but check out this VI.  We can set plot colors with property nodes. I know, this VI is pretty sloppy, but it shows basically what I mean.  See if you can get what you want out of this idea.