Tom, Thanks for your useful response.
Here in the desert (and especially during the southwest monsoon) dewpoints are scrutinized carefully for trends showing surface moisture surges. I write mostly in Python and Perl and do additional analyses such as average daily dewpoint (not shown in the standard NOAA-format tables produced with Weewx) as well as 24-hour trend charts using SQL calls and Gnuplot (example: http://satwatcher.us/wxstation/trend/). I do use standard sprintf calls to format the output but I just always felt it strange to have to do that when the temperature was nnn.n format. Also, as a scientist it just rattles me every time I see a number with too many significant figures. :-) Lastly, I'm interested in the resulting reduction of the size of the database file for efficiency. On a related note, I do see a lot of variation in the dewpoint trace, often jumping 1 or 2 degrees back and forth. As a meteorologist I do understand that dewpoint typically has a higher variability than temperature but I don't think it's that much, with the sole exception of a sudden wind shift or gust of wind. Now you got me thinking if maybe making this change will actually lead to a more stable value for dewpoint. I will try this change and let you know what happens. Thanks, Ken On Sun, Aug 16, 2020 at 4:24 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 >> >> -- >> You received this message because you are subscribed to the Google Groups >> "weewx-user" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/weewx-user/20d1b87c-afd9-4f1c-b00c-88f9011057d8n%40googlegroups.com >> <https://groups.google.com/d/msgid/weewx-user/20d1b87c-afd9-4f1c-b00c-88f9011057d8n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "weewx-user" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/weewx-user/CAPq0zEBuz-FwYAt2z6YT4mZ39WipiBhLny4zwnbd3FZYkRci1Q%40mail.gmail.com > <https://groups.google.com/d/msgid/weewx-user/CAPq0zEBuz-FwYAt2z6YT4mZ39WipiBhLny4zwnbd3FZYkRci1Q%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "weewx-user" group. 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