Radiation units in WH3081

[Elton Prytz]

Hi

The WH3081 has radiation and UV sensors. The data shown on wunderground is correct for the UV Index but the radiation data appears to be sent as lux whereas wunderground is expecting W/sqM.

The console sends the data as lux and it does not matter what units are set for the console display.

Regards
Elton

[mwall]

elton,

pywws uses a simple multiplicative conversion to go from lux to watts per meter squared:

wm2 = lux * 0.005

this is just an approximation - a proper conversion from luminosity to radiation requires more inputs.

to try this approximation, put this in the StdCalibrate section of weewx.conf

radiation = radiation * 0.005

does that bring your luminosity numbers close to the radiation numbers expected by wunderground?

m

[Elton Prytz]

Hi Matthew

I used a multiplier of .001464 which I obtained from a Google search (683lux = 1wm2).  Using this conversion gives the same result as what is displayed on the console when it is set to display in w/m2.

I put this into the section "Keymap" in fousb.py as this seemed to be where the conversions were done from whatever units the console sends to the units used in weewx.

i.e.

keymap = {
    'inHumidity'  : ('hum_in',       1.0),
    'inTemp'      : ('temp_in',      1.0), # station is C
    'outHumidity' : ('hum_out',      1.0),
    'outTemp'     : ('temp_out',     1.0), # station is C
    'pressure'    : ('abs_pressure', 1.0), # station is mbar
    'windSpeed'   : ('wind_ave',     3.6), # station is m/s, weewx wants km/h
    'windGust'    : ('wind_gust',    3.6), # station is m/s, weewx wants km/h
    'windDir'     : ('wind_dir',    22.5), # station is 0-15, weewx wants deg
    'windGustDir' : ('wind_dir',    22.5), # station is 0-15, weewx wants deg
    'rain'        : ('rain',         0.1), # station is mm, weewx wants cm
    'radiation'   : ('illuminance',  0.001464), # station is lux weewx wants W/M2
    'UV'          : ('uv',           1.0),
    'dewpoint'    : ('dewpoint',     1.0),
    'heatindex'   : ('heatindex',    1.0),
    'windchill'   : ('windchill',    1.0),
}

Regards
ELton


 

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[mwall]

elton,

thank you for validating this.  i have added your change to fousb.py

m

[Hugo Valentim]

I am not sure that mimicking the console readings is the best option since they are pretty pointless and would make sense only if the sensor was able to do direct readings (I mean to track the Sun).

To deliver an estimate of global horizontal irradiation one should use instead a multiplier of 0.0079. This is actually also the figure being adopted by other weather apps, such as Cumulus and WD.