RF Powermeter - Precision

As described here, I've build an RF Powermeter.

The basic firmware is now running. So I started analysing the accuracy of the used meter head.PowerDev


First I made a simple value table  showing the ADC values over power input:  PowerChart (Y Axis must be inverted!)

Applying a linear formula PowerLin shows slight deviations.


A third order polynom show a mucht better match PowerPoly3 PowerDev

All images are screenshots from Ulrich A. Maassen freeware application Polynom Maker Univariante Regression. A similar online application can be found here. The online version shows the coefficients in a much higher resolution.