On Wednesday, 3 April 2019 09:37:32 UTC-3, kobuki wrote:
>
> *Temperature and humidity are independent values.* *There is no direct
> relation between the two*.
>
Kobuki,
I know, you mentioned that before. :-)
I work with the following data:
1. Raw humidity values as received in the weewx-rtldavis driver. Not sure
about the hi-bits because one byte always had value 0x85; for now I assume
the right nibble (5) are the hi-bit part of the raw humidity value.
2. Values received from the Vantage driver, both humidity and outTemp
values.
We know the Davis console and the rtldavis.go program will receive the same
radio-signals from the ISS, so the raw message codes for both are equal.
We then take a group of samples with the same raw humidity value.
They all should have the same humidity % value as presented by the Davis
console, which is read by the Vantage driver. Shouldn't they?
But, they have not!
For samples with all the same raw humidity value, the samples with the
higher percentage presented by the Vantage driver have also a higher
temperature value.
That's why I presume a relation between the two.
Luc
PS. I noticed the same behaviour for the soil-moisture and leaf-wetness
sensors. By experiment I detected norm factors to compensate for
temperature influences.
See the code below:
# soil moisture potential
# Lookup soil moisture potential in SM_MAP
norm_fact = 0.009 # Normalize potential_raw
soil_moisture = lookup_potential(
"soil_moisture", norm_fact,
potential_raw, temp_c, SM_MAP)
# leaf wetness potential
# Lookup leaf wetness potential in LW_MAP
norm_fact = 0.0 # Do not normalize
potential_raw
leaf_wetness = lookup_potential(
"leaf_wetness", norm_fact,
potential_raw, temp_c, LW_MAP)
