ET Evaporation calculations - differs significant with reading from VP Pro2 console

[fraban]

Hi all

I recognized a problem here with my ET readings with weewx and "meteostick".  

We have several VP PRO 2 active plus stations and with ET we see different values. 

Actually today we can see ET value 1.8mm on the Vantage PRO 2 console, but still weewx - we use 3.7.1 and 3.6.2 we have "0"  

Also the value ET we export to our network will be "0"  

I mirrored one system so you can see that ET is zero:  

https://api2.weather365.net/wx85375-02/            max reading is 0.1  today here //   VP PRO 2 console has a value of 1.8mm 

also the ET value export to our network here is 0.    

https://stations.weather365.net/#/station1   

Any idea whats going wrong here-  May be it´s 10 time too low ( magnitude error ? ) 

Thanks for checking 

- frank

[Thomas Keffer]

The Vantage emits a value of ET only once an hour. The rest of the values will be zero. So, if you check "current" conditions, only the one at the top of the hour will be non-zero.

Because of this, the "current" value of ET is not very useful. You really have to aggregate over a day.

-tk

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[Luc Heijst]

Hi Frank,

I can't check my ET values on the Davis console because the solar sensor is connect to my Anemometer Transport Kit which values can be read by the Meteostick driver, but not by the Vantage driver.

The Davis console show the ET DAILY value whereas weewx show the ET values per archive period (typically 5 minutes).

To compare the two values we should totalize the weewx ET values per day I think.

Cheers, Luc

[Frank Bandle]

Yes - still if I look in the database and add the values - at the end of the day its ten times less then the VP PRO 2 console reading.

-frank

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[Thomas Keffer]

It's too early in the day here to get a daily total ET, but my monthly value matches what's shown on the console perfectly.

SELECT SUM(ET) FROM archive WHERE dateTime>1493622000;

-tk

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[Frank Bandle]

I will check and look at it in the next days - database and values exported.

-frank

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[Thomas Keffer]

I just had a chance to check the daily sum. It also matches what's being shown on the console.

One other thing: the console can display total ET in either inches, or millimeters. Make sure the unit matches what is in your database.

-tk

[Frank Bandle]

Thomas

yes we still checked the sum too and it seems that its working. So I guess we can close this issue. I got similiar values here on my 5 weewx stations and it matches with 2 VP Pro 2 consoles . We still test with 2 other stations here in the network. I think it works and our receivers read the values every 5 minutes and not only 1 time a hour. So I had the wrong values I compared in my first view. Thank you 

-frank

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