Author Topic: Ecowitt WS68 UV calibration  (Read 1860 times)

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Offline Topcat

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Ecowitt WS68 UV calibration
« on: April 03, 2020, 07:09:36 AM »
Hi
Can anyone assist on calibrating the UV / solar readings. Mine seem extremly high currently showing 8/824 and its partly cloudy. I checked some nearby stations that seemto be a lot lower
Its been up and running for nearly 2 weeks now.

current readings can be found at https://theforsters.me.uk

Thanks


Offline Mandrake

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Re: Ecowitt WS68 UV calibration
« Reply #1 on: April 03, 2020, 02:19:43 PM »
I would suggest that you contact Lucy (support@ecowitt.com)
Whilst you can apply an offset in Calibration page for the solar radiation setting your station would suggest something is very wrong.
Check that you have not accidentally applied an offset (it should be 1.0)

At this time of year in the UK you should not really see more than 6-7 max.
You may however see a spike if you have water droplets on the sensor as they act as magnifying lens. Not much you can do about those other than keep the sensor clean.
Retired: Old Maplin N96Y/FO Weather station
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Offline Topcat

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Re: Ecowitt WS68 UV calibration
« Reply #2 on: April 04, 2020, 07:55:55 AM »
Hi Mandrake
Thanks for the response. Checked offset and its set at 1.0. I will email Lucy to see if they will ship a replacement. The rest is all working fine.
I might reposition unit to see if it makes a differnce, im not sure but sunlight might be refecting towards it from a neighbours green house but then it would not be all day due to sun position, could that be an issue? unit is at a height of about 6 metres currently until i mount on the roof.

Regards
N

Offline Mandrake

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Re: Ecowitt WS68 UV calibration
« Reply #3 on: April 05, 2020, 05:20:57 AM »
Its possible that reflected Sun might be an issue.
I have been recording a max of about 7 around the middle of the day in the current fine weather we are having in the south.
Retired: Old Maplin N96Y/FO Weather station
G1ZFO

Ecowitt HP2551A + WH65 Tri-Wing (Wunderground: IGUILDFO67)
Ecowitt GW1000 (Wunderground: IGUILDFO68)
Ecowitt GW1000 (Mk2) test environment driving CumulusMX on a RPi 3b
Ecowitt WH51 (x6) Soil Moisture Sensor
Ecowitt WH41 PM2.5 AQM Sensor
Ecowitt WH31 (x8) Thermo/Hygro Sensor
Ecowitt WS80 Ultrasonic Anemometer (pre-prod test)
Ecowitt WH57 Lightning Sensor (pre-prod test)
Ecowitt WH32-EP (SHT35) + Davis 7714 Screen
Ecowitt WH45 CO2/PM2.5/PM10 (production Test)

Offline GeraltLK

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Re: Ecowitt WS68 UV calibration
« Reply #4 on: April 05, 2020, 06:10:06 AM »
However, I have observed that all Fine Offset devices have very high UV values compared to nearby Davis stations. For example, my station and others in my area (Fine offset clones too) gave UV values of 6-7 in February. Davis stations in my area on those same dates never exceeded a UV value of 3.

My station (February):


Nearby Davis station (February)


In March the same. My station values 9-10 many days, Davis station maximum values of 5

I don't understand what this difference is, maybe it will be the sensor, but it is not something that bothers me  :grin:

Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #5 on: April 05, 2020, 06:30:49 AM »
It looks like the Fine Offset UV sensors are of poor quality. At Awekas.at, almost all Fine Offset stations have UV sensors blocked.
I have introduced UV calibration = 0.55 at my stations.
Currently UV = 7 in the UK is a bit too much. How much will your station show in the summer?
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #6 on: April 05, 2020, 06:39:39 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #7 on: April 05, 2020, 06:48:24 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #8 on: April 05, 2020, 08:18:19 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.

Sorry  ;)

Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #9 on: April 05, 2020, 08:35:04 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.

Sorry  ;)

Mauro, write what Your UV readings look like.
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline Topcat

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Re: Ecowitt WS68 UV calibration
« Reply #10 on: April 05, 2020, 08:40:10 AM »
So to eliminate any glass refections unit now moved and mounted at approx 8 meters above ground level. sensors are clean no signs of any moisture.
So just after midday I see UV of 8 and solar of 877 w/m2 so i should be burnt to a crisp  :grin:
I guess i can try to adjust offset to get a more realistic figure. I did some research and as Mandrake says 7 max for the UK in the middle of summer and that would be a rare reading average is 5-6 in the hieght of summer in the south.
Does the Solar reading look more realistic.

Regards
N


Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #11 on: April 05, 2020, 08:52:41 AM »
On page:
http://www.meteovista.com/Europe/United-Kingdom/Sunpower-London/4163337
there are today's maximum UV values for Great Britain.
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #12 on: April 05, 2020, 08:53:01 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.

Sorry  ;)

Mauro, write what Your UV readings look like.

I have to admit that I never gave importance to this parameter, but only because I don't care
having said that, I believe that my ws80 overestimates this parameter, today often has touched the value of 7

Mauro

Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #13 on: April 05, 2020, 09:04:41 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.

Sorry  ;)

Mauro, write what Your UV readings look like.

I have to admit that I never gave importance to this parameter, but only because I don't care
having said that, I believe that my ws80 overestimates this parameter, today often has touched the value of 7

Mauro

By page:
http://www.meteovista.com/Europe/Italy/Sunpower-Italiani/4864373

in Italy, UV should be between 3 and 5, and around 3 to 4 in your area.
Could Fine Fine Offset UV sensors be of poor quality?
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #14 on: April 05, 2020, 09:11:46 AM »
My ws80 Ecowitt is ok compared to Davis Vantage pro, same exposition

last two hours, no offset

 [ You are not allowed to view attachments ]

Here we write about the UV sensor. You give a comparison of a solar sensor. These are two different things.

Sorry  ;)

Mauro, write what Your UV readings look like.

I have to admit that I never gave importance to this parameter, but only because I don't care
having said that, I believe that my ws80 overestimates this parameter, today often has touched the value of 7

Mauro

By page:
http://www.meteovista.com/Europe/Italy/Sunpower-Italiani/4864373

in Italy, UV should be between 3 and 5, and around 3 to 4 in your area.
Could Fine Fine Offset UV sensors be of poor quality?

In my opinion, every entry-level weather station use low cost and low-quality sensor.
for some parameter, like temperature, humidity, wind, rain, barometric pressure, there's no problem, now it's possible to have very good performance with very low cost sensors, but there are some parameters, like UV, that need something other, more professional, more accurate etc

Mauro

Offline krojan

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Re: Ecowitt WS68 UV calibration
« Reply #15 on: April 05, 2020, 09:19:21 AM »
If a sensor is already installed, it should show real values. Overstating by 200% or 300% is a misunderstanding.
Sorry for my English.
GW1000, HP2551-C, HP3001, HP1001.

Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #16 on: April 05, 2020, 09:26:43 AM »
If a sensor is already installed, it should show real values. Overstating by 200% or 300% is a misunderstanding.

in fact I always thought that a weather station should have all the sensors separate
I will only choose the sensors based on the parameters that interest me, in fact my main stations are like this, these are toy stations and must be taken for what they are, for certain things they can also go well, for others not

Mauro

Offline Mandrake

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Re: Ecowitt WS68 UV calibration
« Reply #17 on: April 05, 2020, 01:39:44 PM »
well I admit I tend to use these as indicators as far as solar UV is concerned
For reference my WH65 (Triwing sensor) recorded 480 w/m3 (UVI 4)
My WS80 which is 2 feet away recorded 667 w/m3 (UVI 7)
This is for a cloudless sunny day in the south of the UK today

I am more inclined to believe the WH65 though in most aspects the WS80 is the superior instrument for everything else
I have not tried calibrating the UV sensor as it seems to be more of an indicator than anything else.
I must admit I have done any research in the sensor accuracy or discussed this with Lucy.
Retired: Old Maplin N96Y/FO Weather station
G1ZFO

Ecowitt HP2551A + WH65 Tri-Wing (Wunderground: IGUILDFO67)
Ecowitt GW1000 (Wunderground: IGUILDFO68)
Ecowitt GW1000 (Mk2) test environment driving CumulusMX on a RPi 3b
Ecowitt WH51 (x6) Soil Moisture Sensor
Ecowitt WH41 PM2.5 AQM Sensor
Ecowitt WH31 (x8) Thermo/Hygro Sensor
Ecowitt WS80 Ultrasonic Anemometer (pre-prod test)
Ecowitt WH57 Lightning Sensor (pre-prod test)
Ecowitt WH32-EP (SHT35) + Davis 7714 Screen
Ecowitt WH45 CO2/PM2.5/PM10 (production Test)

Offline galfert

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Re: Ecowitt WS68 UV calibration
« Reply #18 on: April 05, 2020, 04:51:55 PM »
For Fine Offset stations the UV and Solar Radiation all comes from the very same sensor. It is a Lux sensor. This then gets converted to both UV and Solar Radiation based on some predetermined formulas.

That said we do have the capability to make calibration adjustments as Krojan has done.

Davis VP2+ stations have separate UV and Solar Radiation sensors that are of much higher quality.

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Offline Topcat

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Re: Ecowitt WS68 UV calibration
« Reply #19 on: April 06, 2020, 05:07:11 AM »
I have emailed Lucy so will see what they say.
In the mean time how would you go about calculating what offset to apply to make reading more realistic. I note in the manual it says to recalibrate Solar/UV every 2-3 months but no instructions on how you would do this.

Regards N

Offline Felixus

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Re: Ecowitt WS68 UV calibration
« Reply #20 on: April 07, 2020, 03:30:26 PM »
On my Osprey sensor the reported UV Index is double to what it is on the nearby Davis Vue Pro station, so I applied offset of 0.5 to my GW1000 and the readings coresponding with Davis station and to the predicted UVI for my location. I only noticed that after reading this post.
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Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #21 on: April 07, 2020, 04:06:21 PM »
We are comparing the UV result in a lot of Fine Offset stations in our network and had found that an offset of 0.65/0.7 can give a result with good accuracy compared to official maps and Davis UV sensors
this comparison work will continue next days thank to the good weather conditions

Mauro

Offline galfert

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Re: Ecowitt WS68 UV calibration
« Reply #22 on: April 07, 2020, 08:10:19 PM »
I don't want people to take anyone else's recommendation of what is a proper UV or Solar Radiation calibration adjustment number. The reason being that the calibration required is going to be very different for people living in different parts of the world. These stations use a Lux sensor and they try to approximate Solar Radiation and UV based on some loose definition of how much radiation there is in visible light. This is going to differ if you live in Italy versus the UK and it will differ if you live in different parts of the US.

Therefore please do not go by anyone else's calibration recommendation... Unless you live where they live AND you really trust them.

The simple explanation is that these stations don't have a real Solar Radiation and UV sensor. They have a Lux sensor which is a different animal and FO is trying to deliver Solar Radiation and UV by making some broad assumptions on Lux.
« Last Edit: April 07, 2020, 08:14:15 PM by galfert »
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Offline mauro63

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Re: Ecowitt WS68 UV calibration
« Reply #23 on: April 08, 2020, 02:41:28 AM »
I don't want people to take anyone else's recommendation of what is a proper UV or Solar Radiation calibration adjustment number. The reason being that the calibration required is going to be very different for people living in different parts of the world. These stations use a Lux sensor and they try to approximate Solar Radiation and UV based on some loose definition of how much radiation there is in visible light. This is going to differ if you live in Italy versus the UK and it will differ if you live in different parts of the US.

Therefore please do not go by anyone else's calibration recommendation... Unless you live where they live AND you really trust them.

The simple explanation is that these stations don't have a real Solar Radiation and UV sensor. They have a Lux sensor which is a different animal and FO is trying to deliver Solar Radiation and UV by making some broad assumptions on Lux.

we are not doing this, we are telling our users
"hey, the UV data on the map of your station are not realistic compared to the official station that you can find at the following link ...... and to those of the official maps that you find at the following link ......
try to apply an offset, starting from this example value until you have a data as close to the official one "

it is very different

Mauro

Offline galfert

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Re: Ecowitt WS68 UV calibration
« Reply #24 on: April 08, 2020, 08:54:38 AM »
Mauro63,
I agree that you are not telling people to use your calibration unless they are near you. I was just trying to make it clear to others that may stumble on posted calibration offsets and blindly accept them.
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Windy: pws-f075acbe
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anything