In this post I describe in details, how you can create the calibration factors for k0 ... k3 based on raw data measured with the power sensor.
Center is this XLS file. Relevant are lines 27-37.
Column A contains the power provided by the generator. These must be either in descending or ascending order.
Column B contains the raw value from the ADC (therefore we have this third screen in V1.7.1)
Column J contains the corrected values based on the factors k0-k3
Column K shows the absolute difference to the generator output level
So now, how to get the factors k0-k3? Goto http://www.xuru.org/rt/PR.asp#Manually
This is one solution. Enter the values k0=x^0, k1=x^1, k2=x^2, k3=x^3 into the config utility at the desired frequency line and smile ;-)
To get an idea, how the created factors match the ideal line, you can enter them into the XLS cells J24 ... M24 and you get a graph showing the deviation from the ideal line.