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# [SOLVED]Interpolation/function identification

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#### LaszloF

##### Member level 2
Dear Sirs,

I want to measure temperature with some NTC's.
The nature of these isn't linear, in the datasheet there is a table for resistance values in 5C(degree Celsius) steps. From that data i need to get a function, or make some type of interpolation, the measurement needs have 0.01C resolution.

What do you suggest? Is it even possible to make this?

Hello LaszloF,

The best way to do tthat with the finest accuracy is to use a spline interpolation of your points. Take a look at :
http://en.wikipedia.org/wiki/Spline_interpolation

The algorithm to use for it is simple to implement. You can take an example in the Numerical Recipies. See in: http://www.nrbook.com/a/bookcpdf.php
the chapter "3.3 Cubic Spline Interpolation 113"

Good luck!

Cheers,

Elvis

LaszloF said:
Dear Sirs,

I want to measure temperature with some NTC's.
The nature of these isn't linear, in the datasheet there is a table for resistance values in 5C(degree Celsius) steps. From that data i need to get a function, or make some type of interpolation, the measurement needs have 0.01C resolution.

What do you suggest? Is it even possible to make this?

### LaszloF

Points: 2
First of all, thanks Elvis, i will look into it, meantime i found a linearization method for NTC's, it's called the Steinhart-Hart equations.

But for a general solution I will use the spline interpolation , i will try to compare the two methods on NTC's and post a feedback.

Regards,
Laszlo

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