Callendar-van Dusen when I don't have extreme high and low temps

[GregFreeman]

I am currently trying to use a method from the following document to calculate the coefficients alpha, delta, and beta, and ultimately A, B, and C for an RTD ftp://ftp.hartscientific.com/manuals/9933.pdf. See section 3.8.1 - 3.8.3 (inclusive).

This method is used in some hartscientific software and it gives the user the ability to get these coefficients for over-constrained system of equations even when they haven't taken data at very large and small temperatures (like you normally do to get the 4 temperatures necessary for the CVD equation).

Please see the attached snippet for data. The setpoint array is the temperatures and the data array is the resistances. When I put these values into the hart scientific program I get alpha, beta, and delta to be alpha = .003853
delta = 1.34112, beta = 4.5563.  This gives me A, B, and C to be A = .0039, B = -5.16 E -7and C = 1.7 E -10

I am trying to use this method to get these values in LabVIEW but to no avail. I also tried to go straight to A, B, and C rather than calculating alpha beta and delta first (shown in snippet) but that didn't work either. Does anyone have suggestions for what I'm doing wrong, or what I can do to get these coefficients?

Let me know if you need clarification, I know that was a bit confusing. Essentially what I want is to have the calculated coefficients in my LabVIEW code to match the coefficients calculated by the hart scientific program for the supplied data.

 

[GregFreeman]

I think I have gotten it (at least I got A and B, so C shouldn't be too hard). I will post my solution once I have it all figured out. Just hoping to save some time for anyone that may have decided to work on this.

[JtotheB]

Hey for(imstuck),

I'd be interested in seeing this complete code. There is another implementation that I found where someone did these calculations using a formula node, rather than straight graphical programming. You can find that implementation here if you are still stuck finding the last coefficient. Hope that helps!

[GregFreeman]

Here is my method I have been trying based off the hart scientific software. With the default values I have in the controls I get respectable numbers. However, the comment on the front panel has another set of data and the output from the other software, and when I plug those numbers into my program, I get no where near their solution.

Any mathematicians out there?