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How to Output Values into an Array?

Please Help.


I am trying to create a fancurve model for an HVAC system in LabVIEW. The trouble I am having is initializing my array to take in 17 iterations, as well as displaying the output into an array. I am not sure if using the formula node is the best option for my code but everything seems to work except the array.



Thank you

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Message 1 of 13

Hi Austin, please upload for an older version (say LV 2012) using the File >> Save for previous version... buttons.

Message 2 of 13

here is version 12

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Message 3 of 13

Let me start by saying that I don't think I've used a single formula node in any of my programs, but I think I see your confusion of arrays. 

  • Each time the formula is run you will calculate a value DP. To get the array of each iteration's result, simply wire DP over the edge of the for loop. You will get an auto-indexing tunnel with the array at the output. 
  • For the input, it looks like you are using "i" as an index in your calculation. In that case, get rid of the initialize array stuff. Just wire the "i" from the for loop into the "i" of your formula. Get rid of the line in your formula which sets i equal to an array.
  • I don't know why Density and VFR are built into 2D arrays, as it looks like you only use a single index in your formulas. I would get rid of those 2 build arrays. Better yet, take Density and VFR outside of the for loop and wire them in through an auto-indexing tunnel, it will do the indexing for you. Then get rid of the [i] in your formula.
  • Waveform chart is meant to take points as you read them, so you could update this inside the loop. 
  • Waveform graph is meant to take an array of points, so update this just outside the for loop.
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Message 4 of 13

Fairly close and some fundamental misunderstanding on formula node. I've tweaked it some, you created 2D arrays and sent in dummy variables which isn't needed.

Formula node'.png


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Message 5 of 13

@Yamaeda wrote:

Fairly close and some fundamental misunderstanding on formula node. I've tweaked it some, you created 2D arrays and sent in dummy variables which isn't needed.

Why not just autoindex on the input arrays with the FOR loop? Then you don't need the i input to the formula node.

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Message 6 of 13

But the code needs to run for multiple values of VFR ( from 0 to 4000 in increments of 250). So how wouldn't I use VFR in an array? I created density as an array because the code did not like me using one value for an array.

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Message 7 of 13

It would still be an array, but you pick off each element by passing it through an auto-index terminal. You are currently indexing inside your formula node with "[i]" notation. You could also do it with "index array" in LabVIEW. Or you can use the auto-index terminal. The following 3 pieces of code give you the same result, but the auto-index terminal makes it much neater.



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Message 8 of 13

Insert image wasn't working earlier, here is the snippet:



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Message 9 of 13

I understand the auto-indexing now. Thank you. But I am still having trouble generating the VFR array from 0-4000 in increments of 250, to generate and then graph an output of DP(delta pressure). The Code did not break on me, but it's not generating an output. I have attached my block diagram and front panel.

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Message 10 of 13