Topic: Is my Atlas UV sensor defective?

[MacGarage]

My third (!) Atlas replacement sensor only went to 2 no matter what. I kept the repaired lightning unit from the third unit and the UV part on the second one to create a fully working unit. Now, my current unit has measured up to 8 in the recent spring days.

[Mirwin275]

I live in South Florida and the highest mine has ever reached is a 6 twice.  There is definitely something wrong along with the lightning detector that shows daily lightning and the rain gauge that very much under reports.  I am quite disappointed with the Atlas so far.

Here is a screenshot from the EPA's website for today's forecasted max uv readings. It looks like you should be reading between 9 and 11 for your max today. [ You are not allowed to view attachments ]

[DoctorKnow]

Mine hit 5 today. Seems reasonable. My Beta model never went over 3.

[wase4711]

outside of Phoenix, my Davis UV says its 10 today, as does the US EPA....
I was never able to get an accurate UV number with the Atlas when I had one, and my Ambient station was usually pretty close to what the EPA map said..

[DoctorKnow]

I'll have to take a good look at the sensor. Maybe it is too well shielded with the design, or maybe it needs to be angled?

[wxmanfla]

I live in South Florida and the highest mine has ever reached is a 6 twice.  There is definitely something wrong along with the lightning detector that shows daily lightning and the rain gauge that very much under reports.  I am quite disappointed with the Atlas so far.

Here is a screenshot from the EPA's website for today's forecasted max uv readings. It looks like you should be reading between 9 and 11 for your max today. [ You are not allowed to view attachments ]

Based on the map I should have reached a 10.  Today the max was 5. 

[DoctorKnow]

It appears there is some sort of white piece of shielding under the plastic housing of the UV sensor... I am wondering if it is filtering too much light off the sensor?

Thoughts? I had a fine offset UV sensor, and it was frosted over to filter the light. The white shield on the Atlas is quite solid.

[MacGarage]

I was comparing my Fine Offset to the Atlas and when the Atlas was stuck on 2, the Fine matched what others were reporting while the Atlas was on 2. Now that I have the Atlas working, both normally read close to the same.

[nincehelser]

If I remember the manufacturer’s docs, it is a place of transclusent Teflon to reduce the intensity of the light

[DoctorKnow]

nincehelser,

Do you think we could try to remove it, or would we break it?

[nincehelser]

nincehelser,

Do you think we could try to remove it, or would we break it?

It's removable with your fingertip, but the black circular gasket will come with it.  How easy it is to get back in place is another matter... maybe it will sit securely by itself.  I'm not sure what problems tacking it back down with CA glue would cause.

[DoctorKnow]

Mine wasn't glued. It was very easy to take out, and put back.

[Mirwin275]

I would keep it in. It reads way high and really out of wack without it in. There's a reason it's there, but maybe it obstructs the sensor too much with the material they used to filter so it's not so sensitive. I suppose that is the purpose of it.  [ You are not allowed to view attachments ]       [ You are not allowed to view attachments ]

[DoctorKnow]

I didn't take it out.

[Mirwin275]

I didn't take it out.

Yea, keep it in then. I still think the Atlas under reports for uv though.

[nincehelser]

Here's the application doc for the sensor:
https://www.silabs.com/documents/public/application-notes/AN968-Si1133-UV-Index-Sensor-Electrical-and-Optical-Design-Guide.pdf

From my reading, the "dot" is called the "diffuser", and the plastic cap is referred to as the "overlay".

It does sound like you want the diffuser in place for the best accuracy.

 [ You are not allowed to view attachments ]

[Mirwin275]

Here's the application doc for the sensor:
https://www.silabs.com/documents/public/application-notes/AN968-Si1133-UV-Index-Sensor-Electrical-and-Optical-Design-Guide.pdf

From my reading, the "dot" is called the "diffuser", and the plastic cap is referred to as the "overlay".

It does sound like you want the diffuser in place for the best accuracy.

Good info. I just wonder if the diffuser needs to be improved in some way. If it's in, it seems like it under reports. If it's out, it reads all crazy, which I anticipated it would do. Hmm? Just not sure still if it's accurate enough with the diffuser Acurite uses for it?

[Bart]

Resurrecting this topic.

I got my Atlas, and I am too having issues with UV reporting. While being a little low isn't TOO horrible, what bothers me is that there are times throughout the day where UV will briefly hit ZERO (and then return to bouncing between 1 and 2, when other nearby stations are reporting a solid 3 with an occasional 4.

I live in Phoenix, AZ. It was a completely clear sunny day today. At 11:44am I had a reading of zero briefly (among a few other sporadic zeros throughout the day). No way could there have been a zero UV at that time. Checking back over my daily charts (I've only had the Atlas for about a week), I see some instances from other days where I had a zero reading for UV during the day.

I can understand a bit of a LOW reading, but a ZERO? No way.

So anyway....my reasoning for resurrecting this topic. Since I haven't yet taken apart my Atlas to get a good look at parts, has anyone tried making their own diffuser to replace the stock one? Since I don't yet know exactly what the stock one looks like, I can't yet come up with something that may allow a little more light to pass through...but I am trying to think of something that could be made to replace the stock diffuser.

Anybody done anything like this yet to correct the low UV readings?

I did do a test like nincehelser did, and shined a flashlight on the sensor, and it went right up to 15. So, I know the sensor itself is working. It does just seem to me (as others pointed out) that too much light is being filtered by the diffuser.