vp2 rainRate calibration

[Graham Eddy]

moving to a new VP2 (19.5yo one is twitching in its last throes), i have taken the opportunity to re-think everything from first principles

please check my thinking on rainRate calibration in weewx.conf[[Corrections]]:

#GE 2025-08-20 new VP2 - rain calibration.

        # 500ml water sample read as 21.082mm but 23.4mm expected.

        # rain reading low - normal for a new VP2.

        # 'weectl device' has no way to define a gain for rain, so have to

        # apply it as a Correction here

        rain = rain * 1.1101

        #

        # the following rain-related values also come directly uncalibrated

        # from VP2 so we have to apply same gain here

        stormRain = stormRain * 1.1101

        dayRain = dayRain * 1.1101

        monthRain = monthRain * 1.1101

        yearRain = yearRain * 1.1101

        #

        # the following can be derived in [[Calculations]] from

        # Corrected rain (prefer_software) but instead we choose to take

        # them uncalibrated (prefer_hardware) and apply the gain here

        # for simplicity and consistency

        rainRate = rainRate * 1.1101

cheers

⊣GE⊢