X-Scale on Waveform Chart using Property Nodes

[ByrneLab]

Hello, 

Example.vi: I'm having an issue with my Waveform Chart in Labview. What I would like to do with this chart is show some history of data (in my code attempt I arbitrarily set it to 180 seconds but would more likely want to do something like 4 hours) and have a bit of a buffer on the right hand side of the chart so the newest data point isn't popping up on the right axis (again, attempted to set it to 60 s arbitrarily).

EPS.vi: What I would really want to do is have my data start at the left axis of the chart and track to the right for about 4 hours. Then when it hits the right hand side of the screen, that time becomes the LHS of the screen and the 4 hours starts again, but you could scroll back a bit to see old data. I tried coding this as well (I thought it was a simple sweep chart that displayed 14400 seconds of data -  with an offset of 0 and multiplier of 1, then set buffer to 18800), but my x-scale became almost arbitrary and the values in the property box changed when I ran it. 

I have tried to use several other posts on the forums to guide my coding, but nothing I have tried works. I must be misunderstanding something in the property nodes (xscale.offset, xscale.max, xscale.min, xscale.start, etc.), but I can't find anything to help me out. 

From what I can tell on the forums most labview experts hate the DAQassistant but I am doing my best here. 

[altenbach]

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@ByrneLab wrote:

From what I can tell on the forums most labview experts hate the DAQassistant but I am doing my best here. 

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Also, most users here don't have LabVIEW 2024, so I recommend to do a "save for previous" (2019 or below) before posting VIs.

[ByrneLab]

Is this good? I used Toolkit V Picture Control v2. 

[altenbach]

Yes, that's fine. I can open it.

• Since I don't have DAQ installed, I cannot look at any of the express VIs to e.g.  tell the loop rate as configured. What is the loop rate? Unless it matches the axis multiplier of the chart, all bets are off.
• Why do you have a breakpoint on the toplevel diagram? (red boundary). That makes no sense!
• Your chart history is only 1024 points.
• Why is the front panel maximized to the screen? Nobody want to stare at 80% empty grey space.
• If you would wire the error out of the first property node to the loop boundary, you can eliminate the sequence structure because dataflow fully determines the loop rate. Much cleaner! Seasoned programmers don't overuse sequence structures. They are rarely needed.
• There is a lot of over-complicated code, for example compare the two versions of the same functionality below (... and why would you need two "11" constants? One would be sufficient for both places)
• You can eliminate the pressure indicator if you would show the digital display of the chart.

[ByrneLab]

• 
  • These are the DAQ settings. 
• Thank you for letting me know what that was! I must have accidentally pulled up the tools palette at one point and created it. Afterwards, I couldn't figure out what it was to be able to get rid of it. 
• So if I wanted to display the 30 seconds ahead and 180 seconds behind I would need to change the chart length to 210 seconds*2 points/second = 420 points? Is the chart length being longer than the displayed time period a problem? 
• I think what you mean is why make the front panel take up the entire screen when I could make it smaller? I just never bothered with it because it doesn't bother me. 
• I didn't know Max & Min was a pre-written function - thank you for making me aware of it. 
• I've been messing around and moving things around. Once I get a fully functional code I'll try to make it streamlined. I don't have any formal Labview education so I am learning as I am going and don't know all the best practices.