Convert R to Temp

[ppra]

In host of compactRIO controller, how to convert R to temp?

From the read/write FPGA interface, Mod/R0, Mod/R1 FXP of RTD, I can see that on front panel as number, as well as waveform chart of the sensor. However want to change that resistance to temperature. So adding an expression node in Host, have the expression(equation) done for conversion, but how to connect it up. The FXP of RTD1 does not connect as input into the expression node, that I was hoping to output into the waveform chart to see amplitude vs time in temperature degrees, rather than resistance.

How can I do this? Or is there another way to do it? I want to leave it as resistance in the FPGA VI and not convert temp there but in Host instead. Thanks

[GerdW · Accepted solution]

Hi ppra,

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@ppra wrote:

The FXP of RTD1 does not connect as input into the expression node,

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Simple solution: convert the FXP to DBL…

[ppra]

Thanks GerdW.

How do we convert to DBL numeric constant? So change the 'highlighted' FXP to DBL, then use that as input into expression node and wire output into chart.

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[GerdW]

Hi ppra,

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@ppra wrote:

How do we convert to DBL numeric constant?

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I never mentioned any "constants"!

What about a simple ToDBL function to convert your FXP wire into a DBL wire?

[ppra]

Using this ...?

So wire the highlighted FXP that outputs from read/write FGPA interface, wire into DBL then into expression node. That should convert it then? Thank you

[UliB]

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@ppra wrote:

Using this ...?

So wire the highlighted FXP that outputs from read/write FGPA interface, wire into DBL then into expression node. That should convert it then? Thank you

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No. I am sure GerdW is talking about 'To Double Precision Float' function.

https://www.ni.com/docs/en-US/bundle/labview-api-ref/page/functions/to-double-precision-float.html 

[GerdW]

Hi ppra,

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@ppra wrote:

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Did I mention "sparse", "matrix" or "complex double" anywhere in my messages?

No, as Uli wrote, I meant the ToDoublePrecisionFloat.

Use QuickDrop and type "dbl" - for me it's the first item in the list: