Author Topic: Davis LOOP1 vs LOOP2 Data  (Read 467 times)

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Offline galfert

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Davis LOOP1 vs LOOP2 Data
« on: January 13, 2021, 04:25:05 PM »
I'll let others fill in the details that I've left out. But basically starting with Davis firmware 1.90 their loggers now have an option to send out extra data via what is referred to as LOOP2 data. Prior to this firmware you only have access to LOOP(1) data.

The particulars of this could change how your chosen weather software behaves and what data is available. I feel that the biggest gain from LOOP2 data is that your station will be able to send station pressure (atmospheric) to your chosen weather software. Without LOOP2 it is very inaccurate for your software to calculate what your station pressure is. The higher your elevation the worse the results will be. One of the important aspects of your station being able to accurately determine Altimeter pressure is for those that upload to CWOP. Even if you don't upload to CWOP having accurate Altimeter pressure may be important to you.

The problem with depending on only LOOP2 data is that you then might have to do without LOOP1 data that is different if you need what is missing. It depends on how your software works as it may or may not be able to use both LOOP1 and LOOP2 data. Even if you can use both it may be important to realize that some software may behave differently and alternating between LOOP1 and LOOP2 data could signify some issues where depending on what LOOP data is coming in at that moment might trigger for unknown values to be attempted to be calculated....and for Altimeter pressure this would not be desirable as it will fluctuate back and forth between calculated Altimeter and real Altimeter and that most definitely will mess up the data quality. Again different results may be seen depending on software used. These issues may or may not be resolved in various software.

That was all background information. If I have anything incorrect please let me know. The purpose of my post today is to clearly inform Davis users what they are missing if they choose to only depend on LOOP1 or LOOP2. Depending on the types of sensors you have, you may not want only LOOP2. Not only the types of sensors but if you want WeeWX for example to have battery status then you need LOOP1. See the chart below for differences.

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The big reason for this post is because I had not found this information displayed in such a clear manner. Hopefully it helps users deal with LOOP1 and LOOP2 issues and decisions. It will be interesting to see how much of a big deal any of this is and how different software deals with this. According to Tom, in WeeWX you can define for values to not be calculated (use hardware setting) so you can use both LOOP data if you configure it correctly. Not sure on other software and how they work. If all this turns out to me a false alarm...great. At least it will be informative. But it clearly this is an issue that needs attention as many users are probably not utilizing this data in the best means possible.

For anyone still using VVP, or maybe even some older software you should be cautious before upgrading your firmware as you may have compatibility issues where LOOP2 is not able to be used.

Alternative Solution
If this information makes it difficult for you to determine which LOOP data to use or how to better configure your station there is an alternative solution. You can get a WeatherLink Live device as that sends data to your weather software with a totally different protocol that will not be limited in these regards.
« Last Edit: January 13, 2021, 06:43:59 PM by galfert »
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Offline johnd

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #1 on: January 13, 2021, 04:47:33 PM »
LOOP1 and LOOP2 can both be requested simultaneously - no problem in doing that AFAIK - see example on p13 of the Serial Tech Ref. Obviously you need the right F/W in the console and it depends on the software author exactly how/whether this is implemented, but the option is there. Obviously also this only applies to legacy type console loggers.
« Last Edit: January 13, 2021, 04:51:54 PM by johnd »
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Offline galfert

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #2 on: January 13, 2021, 04:50:09 PM »
Yes I realize that both LOOP1 and LOOP2 can be requested....but if the software is not configured correctly then the software may be calculating values that are missing depending on the LOOP being ingested at that moment....and that would be very undesirable.
« Last Edit: January 13, 2021, 04:53:49 PM by galfert »
Ecowitt GW1000 | Meteobridge on Raspberry Pi
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Windy: pws-f075acbe
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Offline GHammer

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #3 on: January 15, 2021, 05:32:48 PM »
LOOP1 has transmitter signal quality in it.
At least, I run LOOP1 and have signal quality.
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Offline mcrossley

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #4 on: January 15, 2021, 06:21:20 PM »
Cumulus uses both loop and loop2 - unless you disable loop2 via the config file, or the firmware is too old to support loop2
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Offline johnd

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #5 on: January 16, 2021, 04:22:06 AM »
LOOP1 has transmitter signal quality in it.
At least, I run LOOP1 and have signal quality.

No sorry it doesn't - wireless quality is not in the LOOP packets. (Though there is a measure of wireless quality in the archive packets and this is presumably what your software is monitoring.)

There are essentially two measures of 'transmitter signal quality' - the % packets received error-free in an interval or time period and the RSSI of the latest packet. I agree that it would have been good for the RSSI to have been included in the LOOP but it isn't. The % good packets received would be difficult to include in a LOOP (except perhaps as a running average or overall % since midnight) because - roughly speaking, since they are two separate processes - one LOOP includes only the latest wind packet data and hence it would be difficult to calculate current reception % from a single value.

So, as far as I'm aware, the only measure of wireless quality passed to software is in the archive packets and not the LOOPs.
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Offline mcrossley

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #6 on: January 16, 2021, 07:37:57 AM »
There is also the reception stats message returned in response to RXCHECK
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Offline johnd

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #7 on: January 16, 2021, 07:56:34 AM »
There is also the reception stats message returned in response to RXCHECK

Mark, out of interest, how often does CMX check this? Hourly maybe? Or more often?
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Sorry, but I can't help with individual issues by email. Please post your issue in the relevant forum section here & I will comment there if I have anything useful to add.

Offline azchrisf

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #8 on: January 16, 2021, 11:17:48 AM »
Does Meteobridge request loop2?
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Offline galfert

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #9 on: January 16, 2021, 11:30:01 AM »
Does Meteobridge request loop2?

Yes Meteobridge supports LOOP2 data since before June 18, 2017. This was done to improve Altimeter calculation accuracy using station pressure that is only available in LOOP2.
https://www.meteobridge.com/wiki/index.php/Forum
Ecowitt GW1000 | Meteobridge on Raspberry Pi
WU: KFLWINTE111  |  PWSweather: KFLWINTE111
CWOP: FW3708  |  AWEKAS: 14814
Windy: pws-f075acbe
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Offline mcrossley

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Re: Davis LOOP1 vs LOOP2 Data
« Reply #10 on: January 16, 2021, 12:31:09 PM »
Mark, out of interest, how often does CMX check this? Hourly maybe? Or more often?

Every 15 minutes.
Mark