HP 1000 and UV-Index

[RothMa]

Hello,

since 2 weeks I have an "HP 1000" weather station of "froggit", similar to "Fine Offset". In the Weewx I use the Observer driver and everything seems to work fine.
Now I've found that the station reports the UV index in uW per square centimeter. These values are stored in the database in the UV field.
How can I calculate from uW per square centimeter to "UV Index" and how can I configure weewx for it?

Thanks for your help.

Martin

[vince]

On Saturday, March 10, 2018 at 9:29:11 AM UTC-8, RothMa wrote:

How can I calculate from uW per square centimeter to "UV Index" and how can I configure weewx for it?

Some quick googling seems to say it might be a little complicated, but I did find one Davis link that might help...

Does https://www.davisnet.com/product_documents/weather/app_notes/93004_306-AN_06-interpret-uv-readings.pdf help any ?

[RothMa]

Hello Vince,

Thanks for the answer. I think it's not easy to convert. In your link, I read, "The index is equal to the EAS-weighted irradiance (in watts / m²) x 40. An index of 10 corresponds to an EAS-weighted irradiance of 0.25 W / m², but if I convert my values this does not fit the index on the display of the station.
At least I think it's easier to adjust the charts and live with the reported values ...

Martin

[vk3...@gmail.com]

In my HP1000 weewx driver, I use the formula (in Python)

int(round(data_value)/256)

where data_value is the value I read directly from the device itself.

The resulting values seem to match those displayed on the console itself.

Susan

[RothMa]

Hello Susan,
Thanks for the answer. I am experimenting with the "StdCalibrate" section in the weewx.conf.
A comparison of the reported values with the UV index according to the console showed the following:
0 = uv <= 100 uW / cm²
1 = uv> 100 uW / cm² <= 450 uW / cm²
2 = uv> 450 uW / cm² <= 900 uW / cm²
3 = uv> 900 uW / cm² <1350uW / cm²
So I entered the formula UV = (UV - 100) / 450 + 1 in the Calibrate section.
But I will also test it with UV = UV / 256.
At the latest in the summer I will have found out, if then the values with the values in the Conole agree.

Many Thanks
Martin