20041Error using Curve Fitting Tool

[thomasjmcpherson]

Hi,

I am trying to read data from a temperature transient captured in a LabVIEW file and use the curve fitting tool to display the fitted output. In the zip file i have added the data files which the vi reads its input from (only use on at at time any one should work). The function model i need to use  and have inputted in the curve fitting tool is a*(1-exp(-x/b))+c 

where:

‘a’ is the temperature set

‘b’ is the temperature constant 

‘c’ Is the initial temperature 

I have put in some values for each and played around with them to see if they make a difference but still getting the same error.

I had a look on the website for some help guidance but didn’t understand it well enough to be able to resolve it. The error code is "-20041 occurred at curve fitting" and the possible reason given is “analysis: the system of equations cannot be solved because the input metric is singular”.

[Bob_Schor]

Ah, my two least-favorite LabVIEW elements -- Express VIs and Dynamic Wires.  Both serve to "simplify" and "obfuscate" LabVIEW operations.

Can you provide a text file or .csv ("Delimited Spreadsheet File") of the data, as well as initial "guestimates" for the fitting parameters a, b, and c?  Are you familiar with non-linear fitting techniques?  Is there one you'd like to try using LabVIEW?  Have you looked at the Fitting Palette under "Mathematics"?

Bob Schor