Alternative method would be to set Vantage driver loop_request to 3 so that
you would get loop1 and loop2 data. Vantage loop2 provides dewpoint to 1
decimal point . Please review User Guide
<http://www.weewx.com/docs/usersguide.htm#[Vantage]> and be sure you
understand how to set it up , further changes are required.

On a system here that is set up to alternate loop1 and loop2 here is a
database query for dewpoint:

sqlite> select datetime(dateTime,'unixepoch','localtime'),dewpoint from
archive ORDER BY datetime desc limit 10;
2020-08-16 20:00:00|62.0
2020-08-16 19:55:00|62.0
2020-08-16 19:50:00|62.0
2020-08-16 19:45:00|62.0
2020-08-16 19:40:00|62.0
2020-08-16 19:35:00|62.0
2020-08-16 19:30:00|62.0
2020-08-16 19:25:00|62.0
2020-08-16 19:20:00|62.0
2020-08-16 19:15:00|62.0

Paul

On Sun, Aug 16, 2020 at 7:24 PM Tom Keffer <[email protected]> wrote:

> Archive records are what are stored in the database. A Vantage station
> produces its own archive record (unless record_generation is set to
> 'software'). However, for whatever reason, Vantage stations do not include
> dewpoint in the hardware generated record, so WeeWX must calculate it. By
> default, WeeWX calculates the average dewpoint seen over the archive
> interval. If dewpoint changes over the interval, the average is not
> necessarily an even number.
>
> One way around this is to have WeeWX calculate the last value seen,
> instead of the average. Add this to the end of your weewx.conf file:
>
> [Accumulator]
>   [[dewpoint]]
>     extractor = last
>
> Alternatively, what sort of external programs are you writing? Does the
> language you are using provide a way to format decimal output?
>
> -tk
>
>
> On Sun, Aug 16, 2020 at 3:16 PM [email protected] <[email protected]>
> wrote:
>
>> Hi,
>>
>> I searched the group for this subject and couldn't find anything so I am
>> posting.
>>
>> I have the Vantage Pro 2, serial interface to Weewx 3.9.2 run on an
>> Ubuntu server.
>>
>> Below is a sample line from the archive database (broke into individual
>> lines due to width) using the command:
>>    sqlite3 -header -csv /var/lib/weewx/weewx.sdb "select * from archive;"
>>
>> One line from the output:
>> 1597612740,1,1,29.617,28.0238601652778,29.7814033867068,83.7,*115.4*,
>> 38.0,18.0,0.0,,1.0,225.0,0.0,0.0,*61.1737982063856*,115.4,
>> 115.4,0.0,,,,,,,,,,,,,,,,,,,,93.9583333333333,0.0,5.31,,,,,,,,,,
>>
>> Note the temperature is reported as 115.4 degs (ugh...this is Arizona).
>> The dewpoint is reported as 61.1737982063856.  All dewpoint values in the
>> database have a decimal precision of 13 places, clearly outside the sensor
>> quality range. The sensor documentation indicates that it provides Relative
>> Humidity values so apparently the console software derives the dewpoint
>> value as it can be displayed on the console. I write a lot of external
>> programs and have to repeatedly reduce the precision for this variable.
>>
>> Is there an easy way to modify my Weewx to store only 1 decimal place for
>> dewpoint or other variables?  I did check /etc/weewx/weewx.conf and could
>> not find any obvious setting for this.
>>
>> Thanks for any assistance,
>>
>> Ken
>>
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