Plotting 2 waveforms on the fly

[marc1uk]

This should be very simple, but somehow i cannot get this to work. I've got a vi that measures temperature, calculates a current based on this, and outputs a new current. It's a PID control, basically. I'd like to plot the T and output I's on a chart. Just add one point at a time to each. I've tried converting to 1D, 1 element arrays, merging the signals, and plotting. I've tried appending that to the existing waveform. Building a 1D array and wiring that into it.... i dunno.

Can someone explain this very simple task please?

thanks in advance

vi attached.

[GerdW]

Hi marc,

- don't use "convert to ddt"...

- use simple charts to display your data and follow the context help saying: "2d data for multiple curves with multiple points"

- don't use so many "value" property nodes

- use shift registers

- don't use so many stacked sequences

Btw. do you know the RubeGoldberg thread?

Conclusion:

Go through the basics course offered by NI and learn to program LabVIEW by dataflow!

[marc1uk · Accepted solution]

Hi Gerd,

Thanks for the reply.

I eventually discovered what i needed in the detailed context help - I just needed to use 'bundle' rather than 'merge' to combine the two new data points and output those to the chart plot.

Spoiler

For some reason though I did need to delete and recreate the chart - it wasn't letting me change the type from a single dbl array to cluster...

Using 'merge' LabView puts the ddt's in automatically.

As for the rest of the vi structure, while I'm sure it could be done better, I don't yet know how - shift registers wouldn't be suitable because i don't want to pass values from one while loop to the next. I've used sequence locals as you can see, but I'm not sure they're any clearer than property nodes, what with the wires all over the place, which you have to flip through the sequence to trace to find out what they are. At least property nodes have labels. And in the case of indicators, I don't know how to do without property nodes when I need to write to a single indicator from many points in my program...? Similar story with the stacked sequences.

Perhaps an example of how something could be done better would help. Maybe when i have some free time I'll spend it going through the Rube Goldberg thread picking up tips.