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Weather Software => Station Software Development => Topic started by: iisfaq on July 31, 2021, 10:06:48 PM

Title: Davis Vantage Pro 2 - Loop2 Packet
Post by: iisfaq on July 31, 2021, 10:06:48 PM

Hi

I am reading the data directly from the Davis Vantage Pro 2 data logger via serial port.

I use to use the LOOP packet and read the data and I decided to use the LPS 2,1 and push this to a RabbitMQ server and then display the wind in near real time (2-3 seconds)

I think the 10 minute wind gust field is not correct as it is does not seem like a wind gust at all. The value is very low.

You can view the live values on my web site at https://weather.crowe.co.nz (https://weather.crowe.co.nz)

Looking at the documentation for LOOP2 at https://cdn.shopify.com/s/files/1/0515/5992/3873/files/VantageSerialProtocolDocs_v261.pdf?v=1614399559 shows the following

Name	Offset	Size	Description
Wind Direction	16	2	It is a two-byte unsigned value from 1 to 360 degrees. (0° is no wind data, 90° is East, 180° is South, 270° is West and 360° is north)
10-Min Avg Wind Speed	18	2	It is a two-byte unsigned value in 0.1mph resolution.
2-Min Avg Wind Speed	20	2	It is a two-byte unsigned value in 0.1mph resolution.
10-Min Wind Gust	22	2	It is a two-byte unsigned value in 0.1mph resolution.
Wind Direction for the 10-Min Wind Gust	24	2	It is a two-byte unsigned value from 1 to 360 degrees. (0° is no wind data, 90° is East, 180° is South, 270° is West and 360° is north)

The issue I have is with the 10 min wind gust, it shows a very low value and does not appear to be related to a wind gust at all.

(https://i.ibb.co/6WWPvSz/Wind-Gust-Bytes.png) (https://imgbb.com/)

The 10 above refers to 1 mile per hour.

(https://i.ibb.co/0htYD6Z/Wind-Speed-And-Dir.png) (https://imgbb.com/)

Note: Image taken at a different time than the bytes shown above.

Is anyone else using the LPS Command and can confirm that the 10 minute wind gust is not correct?

As you can see from the image below the *current* wind value exceeds all values, 2 min avg, 10 min avg, and 10 min gust so I dont know what the value is refeering to but it is not 10 min gust.

(https://i.ibb.co/8by0BCh/Wind-Gusts.png) (https://imgbb.com/)

Chris

Title: Re: Davis Vantage Pro 2 - Loop2 Packet
Post by: galfert on July 31, 2021, 11:25:48 PM

There is an error in the documentation...
https://www.wxforum.net/index.php?topic=22399.0

Title: Re: Davis Vantage Pro 2 - Loop2 Packet
Post by: iisfaq on August 01, 2021, 03:51:57 AM

Thanks for letting me know.

Wow it would be nice if they fixed their docs.

Cheers

Chris