On 22/06/2023 12:57, Greg Troxel wrote:
Mark Fraser <[email protected]> writes:
Looking at this again, I was confusing maxSolarRad_Wpm2 and radiation_Wpm2,
but the reading is still different to what is shown on the weather
station's own display where it is showing 700 W/m² and I'm getting 129.946
W/m² from weewx_sdr.
Running RTL_433 directly is showing Watts/m : 129.95 and Lux :
88753.0
That should be W/m^2.
You should understand whether your station hardware (which you did not
specify) is measuring irradiance in W/m^2 or illuminance in lux. They
are not the same thing and one cannot convert between them without
making incorrect assumptions. However people do. >
https://github.com/weewx/weewx/wiki/Watts-and-lux
https://www.extrica.com/article/21667/pdf
(likely hard to follow if you are not already familiar with the issues)
So:
Does the station have an illuminance sensor or an irradiance sensor?
(Or both?)
It is an Aercus WS3085 and it doesn't say what sensor it is using, the
display allows you to change the units from Lux, w/m2 or fc.
If it has only an illuminance sensor, common in low-end stations that
have any kind of light sensor, and it reports irradiance, then it is
applying some kind of conversion. See what the manual says and if
unsatisfactory, ask tech support. (I'll wait :-)
(Davis VP2 can optionally have an irradiance sensor, but people do not
use rtl-sdr. It also only reports irradiance and does not report
illuminance. So it seems pretty clear that's not what you have.)
Note that rtl-sdr may also have a conversion, and be populating one
field for the other. That you can read the sources of.
The source code of RTL_433 shows this is how it is receiving light data:
// GETTING UV DATA
int uv_sensor_id = (br[1] << 4 & 0xf0) | (br[2] >> 4);
int uv_status_ok = br[3] == 85;
int uv_index = br[2] & 0x0F;
// GETTING LIGHT DATA
int light = (br[4] << 16) | (br[5] << 8) | br[6];
double lux = light * 0.1;
float wm;
if (preamble == SPB)
wm = (light / 1265.8f);
else //EPB
wm = (light / 6830.0f);
Note that there is no reason to expect that the conversion in the
device and in rtl-sdr is the same, and in reality both are wrong,
because strictly there is no conversion.
Something is wrong somewhere.
Always true! In this case, much, but I hope the above will enable you
to understand better what's going on with your system.
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