Loop Packets and Accumulators

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Billy Jackson

Feb 3, 2024, 10:21:40 PMFeb 3
to weewx-development
Hi Y'all,

I wanted to validate an assumption I have about how loop packets work with Weewx.  The reason being I'm working out a rain issue and it's tough to sort if it's the HW or if I'm doing something odd....

For reference, this is for my weatherflow tempest driver https://github.com/livysdad27/tempestWS.   

1.  The driver opens and uses a WebSocket from the weatherflow Websocket endpoint.
2.  It sends rapid_wind messages every three seconds that I use to generate a partial loop packet.
3.  It sends a obs_st message every minute that I use to generate most of the other data including rain.
4.  Rain, via the API is coming in as "mm recorded since last 60 seconds"
5.  These are emitted via genLoopPacket()

The issue is a report that I'm getting from a user who is seeing 4 - 5X the rain value as other nearby weather stations.  I suspect it's a hardware issue but want to make sure I have some assumptions correct before going down that route.

I THINK what happens is...
1.  Every 300 seconds (archive_interval) the loop packets are accumulated into a record to write into the DB for.
  a.  The current five minute readings
  b.  The daily accumulation is updated.

I'm likely getting something wrong and want to make sure I understand before pushing on the hardware as an issue.

Many thanks.


Tom Keffer

Feb 4, 2024, 1:20:28 PMFeb 4
to Billy Jackson, weewx-development
Putting aside the iffy way that the Tempest calculates rain...

The LOOP packet should include rain since the last LOOP packet. If the Tempest is actually emitting rain over the last 60 seconds and there is more than one LOOP packet in that 60 seconds, then the emitted value will be too high.


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Tom Keffer

Feb 4, 2024, 2:14:24 PMFeb 4
to Billy Jackson, weewx-development
You could run weewxd from the command line and see exactly what LOOP packets are being emitted, as well as the resultant archive records.

On Sun, Feb 4, 2024 at 10:54 AM Billy Jackson <livys...@gmail.com> wrote:
Thanks Tom,

Only one packet (obs_st type) per 60 seconds.  One rapid_wind every three seconds but that doesn't include rain.  At this point I'm fairly certain it's the device.... 

Billy Jackson
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