Interceptor 0.40 "skipping rain measurement"

[G Hammer]

I have been having fairly steady rain here and see this come up in the logs.

Aug 13 15:48:32 PlexSrv weewx[14290]: interceptor: MainThread: skipping rain measurement of 0.03: no last rain

Once this happens, the rain total is off for further periods.

For example, once I saw the 0.03 skipped entry here, the rainfall amount stayed at 0.03

Ambient and WU both have a higher amount recorded.

I'll look at this again later as another rain shower hits and see if the total changes and is correct compared to Ambient and WU.

[mwall]

what kind of weather station is this?

do you ever see this other than when weewx starts up?

please be more specific about "the rain total is off for further periods".

the rain values in weewx are delta measurements, but most hardware reports rain totals.  so any driver must have two data points before it can report a value for rain delta.

the message "skipping rain measurement...: no last rain" indicates that the driver got a non-zero value for the rain total, but since it had no previous value it cannot calculate a rain delta.

the message lets you know that some rain data might have been missed.

(btw, one utility function that might be useful for driver developers would be to get the last rain total from the database, if one exists.  then we could use that value instead of just saying "no last value".  almost every driver has to deal with this for rain or any other delta observations.)

if the weewx rain totals do not agree with a canonical reference, you can fix your rain counts by manually adding values to the weewx database

m

[Thomas Keffer]

(btw, one utility function that might be useful for driver developers would be to get the last rain total from the database, if one exists.  then we could use that value instead of just saying "no last value".  almost every driver has to deal with this for rain or any other delta observations.)

Hmm, I guess I don't like that idea so much. 

The last value in the database is likely to be very out-of-date, resulting in an archive record with a big value of rain. That violates our 2nd and 3rd laws for writing a device driver: don't make stuff up.

-tk

[G Hammer]

The station is a AW 2902A

What I meant is that after I see that logged, rain amount for the day never reaches the amount recorded by the console.

From your explanation, this seems to be the correct way for weewx with this station.

[Wifi75]

hello, I have some problem:

Weewx[11635] INFO user.interceptor: using 'totalrainin' for rain_total
May 13 09:41:37 ubuntu-server python2[11635]: weewx[11635] INFO user.interceptor: skipping rain measurement of 0.63: no last rain

I have GW1000 and WS69e station

I don't understand how I can fix this problem. 

[John Kline]

I’m not familiar with your driver, but this doesn’t look like an error.

It looks like, on startup, the cumulative total rain (totalrainin) is being read for the first time.  For all subsequent reads, the totalrainin wil be compared to the previously read value to compute rain delta (i.e., the amount of rain that fell between the last read and this read).

I believe the informational message you are reading is simply stating that this is the first read and thus, can’t compute a delta because there is no previous read.

At least, this is my guess, without knowing the particulars.

On May 13, 2020, at 12:48 AM, Wifi75 <tizia...@gmail.com> wrote:



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[Wifi75]

but yesterday and yesterday it rained a lot and showed me several mm of rain, but in total it is zero

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Grazie

[John Kline]

If you are seeing this message any more than once at WeeWX startup, then nothing I said applies.

On May 13, 2020, at 7:15 AM, Wifi75 <tizia...@gmail.com> wrote:



but yesterday and yesterday it rained a lot and showed me several mm of rain, but in total it is zero

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[Luc Heijst]

Matthew,

The last_rain value is set to None in the driver init section. Each time the driver is started during rainfall we will miss the registered value of the last archive period. Why not write value last_rain to the database and read it back next archive cycle?

Luc

[Luc Heijst]

Tom,

When a check is done on the timestamp of the last_rain value in the database, we could skip using the value when it is too old, e.g. elder than twice the archive period.

Luc