I recently noticed some issues with my weewx database when calculating
average values from the weighted daily sums compared to from the individual
records. For example:
*select avg(outTemp) from archive where strftime("%m",
dateTime,'unixepoch','localtime')=='09';* gives 16.44376...
*select sum(sum)/sum(count) from archive_day_outTemp where* *strftime("%m",
dateTime,'unixepoch','localtime')=='09';* gives 16.44402...
BUT
*select sum(wsum)/sum(sumtime) from archive_day_outTemp where* *where*
*strftime("%m",
dateTime,'unixepoch','localtime')=='09';* gives 12.76334...
I looked into my database in more detail and noticed that some days have a
much higher count and sumtime than others despite the same record count.
Following this discrepancy further, I then noticed that on the days with
the larger sumtime, some of my records had an interval of 300 and some had
a interval of 5.
This brings me to my question. What is the unit of interval in the
database? I had assumed it was seconds (which matches the units of
archive_interval in weewx.conf), so the records with an interval of 300 are
5-minute averaged catch-up records generated through my drivers
genStartupRecords() where I manually specify the interval to be 300
seconds. The records with an internal of 5 are generated from loop packets.
I suspect my issue is that the units of interval is minutes, and therefore
I should change 300 to 5 in my genStartupRecords() function and manually
adjust my database to change all instances of interval=300 to interval=5 (I
have always used a constant archive interval). Before I do this though, can
someone confirm that my thinking is correct?
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