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WLL Indoor sensor accuracy

Discussion specific to Davis weather stations
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ondrapavlik
Posts: 3
Joined: Sun 18 Jul 2021 5:53 am
Weather Station: VP2 + WLL + RaspB3+ + CumulusMX
Operating System: WIN10/Raspbian
Location: Czech Republic

WLL Indoor sensor accuracy

Post by ondrapavlik »

Hi, I am new here and to Davis station. I have finally installed my brand new Vantage Pro 2 with weatherlink live week ago. It works fine, I love it. Now I am working on RaspbPi 3 + CumulusMX. I just want to ask if there is somewhere more information about WLL indoor module and its accuracy?
I have several (yeah I am crazy into it) thermometers, few were calibrated year or two ago and indoor temperature measurements are quite different from WLL indoor module.
WLL measures more than 1 degree (usually 1,2 degree celsius) higher temperatures. Now I dont have acces to calibrated thermometer to check it.
Is WLL indoor module as accurate as ISS sensor or indoor module is like "lets give them some indoor measurements too to look fancier and ask for more money"?
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PaulMy
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Weather Station: Davis VP2 Plus 24-Hour FARS
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Re: WLL Indoor sensor accuracy

Post by PaulMy »

The indoor temperature with WLL is where the WLL is located. I have mine close to computers and other devices, and it shows high because of its location. Can you relocate the WLL and see if that makes a difference?

Enjoy,
Paul
Davis Vantage Pro2+
C1 www.komokaweather.com/komokaweather-ca
MX www.komokaweather.com/cumulusmx/index.htm /index.html /index.php
MX www.komokaweather.com/cumulusmxwll/index.htm /index.html /index.php
MX www. komokaweather.com/cumulusmx4/index.htm

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ondrapavlik
Posts: 3
Joined: Sun 18 Jul 2021 5:53 am
Weather Station: VP2 + WLL + RaspB3+ + CumulusMX
Operating System: WIN10/Raspbian
Location: Czech Republic

Re: WLL Indoor sensor accuracy

Post by ondrapavlik »

I am new to Davis, but not to measuring :) I have reference spot in my living room, as far as possible from windows, radiators, door, where I calibrate my indoor sensors, also my house thermostat is here. This is not the problem. Problem is that I cant borrow calibrated thermometer from my work anymore and recalibrate my sensors as I used to do for years and check where the problem is hidden.
Thats why I am asking what is inside WLL. You can find tons of information about Davis outdoor sensors, but almost nothing about WLL indoor sensor.
I use "hobby" Netatmo and Renkforce indoor sensors, nothing special, but I used to calibrate them once/two times a year, it should not be random numbers and the difference (1,2 °C) between WLL and rest is just too much to ignore.
I guess I will have to borrow some lab calibrated thermometer and check what is going on.

And thinking about that...When I was searching for house thermostat I had some Honeywell thermostat for few days and it has a really nice bug - it was heating a little bit while connected to AC. Central unit (something like WLL) was measuring 28 °C, boiler was shut down all day and we have 16 °C in house :)
prodata
Posts: 317
Joined: Sat 05 Feb 2011 7:13 pm
Weather Station: VP2
Operating System: Windows - all flavours
Location: Littleport, East Cambs, UK

Re: WLL Indoor sensor accuracy

Post by prodata »

The inside temperature accuracy for a Weatherlink Live unit is specified as ±0.3°C.

But I'm not sure how much I'd read into that - these specifications are usually the intrinsic sensor accuracy (ie the accuracy as if the bare PCB was out on a bench with some air current blowing across it). Inside the WLL case, there will inevitably be some extra heat generation and also limited air circulation. So very likely it will read a little high, and also variably so depending on how stable the room temperature might be, how hard the WLL circuitry is being worked at different times etc. You could probably calibrate its readings to be within a degree or two, but it would depend on circumstances.
John Dann
Prodata Weather Systems
Littleport, East Cambs, UK
http://www.weatherstations.co.uk
ondrapavlik
Posts: 3
Joined: Sun 18 Jul 2021 5:53 am
Weather Station: VP2 + WLL + RaspB3+ + CumulusMX
Operating System: WIN10/Raspbian
Location: Czech Republic

Re: WLL Indoor sensor accuracy

Post by ondrapavlik »

I did some measurements and it is like I assumed.
I have now laboratory calibrated hygro and thermometer at home (calibrated to 0, 15, 25 °C and 40, 60, 80%). I put it with Davis WLL in a room with steady temperature, no radiators, no windows, no air movement, for a night and it is clear.
WLL measures 1,8 °C higher temperatures and 5% lower humidity when AC powered than calibrated unit (19,8 °C vs. 21,6 °C, 72 % vs 67 %). After AC disconnection and AA baterry powering the WLL values reached in 1 hour and 15 min exactly same values like calibrated unit in both parameters, temperature and humidity. After AC reconnection, temperature rised, humidity dropped.
The resume is that WLL generates some heat while powered via AC which leads to higher temperature values and lower humidity values. Powering via AA batery leads to accurate values (compared to my laboratory calibrated unit).
Also fluctuation of temperature values can be observed, while values of calibarted unit and other 2 sensors I have used remain perfectly still for hours, WWL values oscilated in 0,4 °C interval (21,4-21,8 °C).

Well, this is quite frustrating. I was laughing at Honeywell Evohome unit, that they release expensive central heating unit with such bug, but here we are, Davis WLL has the same bug.

I will do some measurements in lower temperatures to check if error remains the same (1,8 °C higher), which could be corrected by calibration of WLL, or it varies...
After this, I will confront Davis with my findings. Question is: It is my WLL unit or all WLL units? Should I return it and try another unit?
It is just "gate" for outdoor sensor, I use Netatmo products for indoor enviroment monitoring, but also it cost me 220 Euros, it should work.
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