My apologies. I forgot one important detail. The "[Delta]" section tells
WeeWX how to calculate rain, but you also have to include "rain" under
[StdWXCalculations] / [[Calculations]] in order to get it to do the actual
calculation. It looks like
[StdWXCalculate]
[[Calculations]]
...
rain = prefer_hardware
...
[[Delta]]
[[[rain]]]
input = dayRain
On Sat, Jan 27, 2024 at 9:17 AM Remy Lavabre <remy.lava...@gmail.com> wrote:
> Hello Tom,
>
> I followed your instructions:
>
> 1/“rain” field present in the database
> 2/ “dayRain” field not present in the database
> 3/ My driver returns “dayRain” values and not “rain” values in the
> packetsloop
> 4/ [[Delta]] [[ [rain]]] input = dayRain added in weewx.conf (under
> [StdWXCalculate]).
>
> I did some tests : my driver returns 0.0 for dayRain but unfortunately the
> "rain" field in my database always remains NULL, even after several
> recordings in weewx.conf.
> Shouldn't "rain" field go to 0.0?
>
> THANKS
>
> Le vendredi 26 janvier 2024 à 22:48:03 UTC+1, Tom Keffer a écrit :
>
>> If an observation type never gets reset to zero, you have two choices.
>> 1. Save the value. If you want to know daily use, take the difference of
>> the value.
>> 2. Save the difference. That is, the change in the value over an archive
>> period. If you want to know daily use, you would sum all the small deltas.
>> This is like rain
>>
>> See the discussion *Accumulated vs delta energy
>> <https://github.com/tkeffer/weewx-brultech?tab=readme-ov-file#accumulated-vs-delta-energy>*
>> in
>> the README of the Brultech driver for the pros and cons of the two
>> approaches.
>>
>> It is not necessary to save "dayRain". WeeWX mostly uses "rain". Besides,
>> as you note, it can always be calculated.
>>
>>
>>
>> On Fri, Jan 26, 2024 at 7:06 AM Remy Lavabre <remy.l...@gmail.com> wrote:
>>
>>> And one more question....
>>> Is it absolutely necessary to create a "dayRain" field in addition to
>>> the "rain" field in the weewx.sdb database?
>>> If the database only contains the [rain] field but the Weewx driver
>>> returns a "dayRain" field (cumulative rain over 24 hours since midnight)
>>> with a real value in each packetloop, the class [[Delta]] [[ [rain]]] input
>>> = dayRain will it work??
>>> (the accumulation of rain since midnight is useless to me in a database
>>> field since it is easily calculated)
>>> Sorry for all the questions...and thanks again! ;-)
>>>
>>> Le vendredi 26 janvier 2024 à 15:46:04 UTC+1, Remy Lavabre a écrit :
>>>
>>>> Hello Tom and thank you for your response.
>>>>
>>>> [StdWXCalculate]
>>>> [[Calculations]]
>>>> ...
>>>> [[Delta]]
>>>> [[[rain]]]
>>>> input = dayRain
>>>>
>>>> This will calculate the rain difference between two records in weewx
>>>> sql based on the principle that the counter is reset to zero at midnight ->
>>>> PERFECT FOR THE RAIN 24H !
>>>>
>>>> Small additional question: if we wish to constantly calculate the
>>>> difference between two records values of a meter which *never* resets
>>>> to zero (such as an electricity or water meter), how should we proceed?
>>>>
>>>> THANKS
>>>>
>>>> Le jeudi 18 janvier 2024 à 14:05:10 UTC+1, Tom Keffer a écrit :
>>>>
>>>>> Unfortunately (for you), WeeWX mostly uses observation type "rain",
>>>>> the amount of rain that fell since the last loop packet (what you are
>>>>> calling "instantaneous rain").
>>>>>
>>>>> You should assign the rain since midnight to type "dayRain".
>>>>>
>>>>> Then calculate "rain" as the difference between successive
>>>>> "dayRain" values. While this is a pretty simple calculation, there is an
>>>>> xtype that can do it for you. See class Delta in weewx.wxxtypes
>>>>> <https://github.com/weewx/weewx/blob/master/src/weewx/wxxtypes.py#L586>.
>>>>> To use it, add this to weewx.conf:
>>>>>
>>>>> [StdWXCalculate]
>>>>> [[Calculations]]
>>>>> ...
>>>>> [[Delta]]
>>>>> [[[rain]]]
>>>>> input = dayRain
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Wed, Jan 17, 2024 at 11:47 PM Remy Lavabre <remy.l...@gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Good morning,
>>>>>>
>>>>>> I created a [driver] for weewx to retrieve data from the Awekas API
>>>>>> (my Bresser weather station does not have a USB port).
>>>>>>
>>>>>> This works but regarding the rain, it is not the instantaneous rain
>>>>>> (from a packetloop) that we recover but the rain over 24 hours since
>>>>>> midnight.
>>>>>> Is there a "simple" way to tell WeeWX that the packetsloop rain data
>>>>>> corresponds to the cumulative rain since midnight and not the rain that
>>>>>> fell during the data retrieval interval (the time gap between two
>>>>>> packetsloops) ?
>>>>>>
>>>>>> Thank you so much...
>>>>>>
>>>>>> --
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>>>>>> .
>>>>>>
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