Calculation of Polynomial coefficients

[Phil7]

Hi,

I have issues using the polynomial curve fit function. I have an array of velocities (x axis) and an array of voltages (y axis). I want to do a polynomial curve fit and get the coefficients for the calculations of the voltage into velocity. I gain the data during a calibration and need to use it separately afterwards. I wired the Vi as I see correct, when I use the calculation backwards, it calculates wrong values for the velocity.

In equation, I want the coefficient for:

Velocity = A + B*Voltage + C*Voltage^2+... (Fourth order)

I hope I could somehow explain the problem. I don't see my mistake here so any help is appreciated. Thanks in advance, the Vi is attached.

I am using LV 2014.

[altenbach · Accepted solution]

You need to read the help. You polynomial evaluation requires the best fit coefficients and [X] and does not need any FOR loop. (You hooked it up to the best fit instead of [x])

Try as follows. Works just fine!

[Phil7]

Hi altenbach,

thanks for you advice.

Helped me find the solution!

Best,

Phil