Topic: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD

[ValentineWeather]

So I'm confused. The 7714 passive shield plates come out of the box, black on the underside ? Or you had to paint them?

I painted mine  Flat Black just bottom plate where sensor mounts  and the nearest top plate toward sensor. I used painters blue tape edges around upper plate so only white (no black) was exposed to sun. Instructions on assembly can be tricky. Better to assembly first time then once you figure that out you will understand what parts I painted black.

Oh OK..So it was the Metoeshield that comes black on the underside. I got them confused.
I just looked at the Meteoshield specs and It's a lot smaller than the Davis shields as far as diameter. Inside diameter is ~ 2.56". But if you could mount the SHTxx PCB vertically (as in the cable hanging straight down) you should have ~.5" on either side which would allow you to place the PCB off-center. thereby positioning the sensor about center. This would allow an upward draft through the center with only the Davis filter cap (assuming you use it) in the airflow.  However, horizontal airflow would be blocked. But according to the design intent, and unlike most gill plate shields.. natural aspiration should be a "quasi-spiral-vertical" (Helical) movement, should it not?

I was in contact with Jan at Metoshield about the big stock filter, he thought it would work. Until I get the shield and see not totally convinced so ordered some of the small filters just in case.

[jerryg]

I was wondering the same thing about the big sensor blocking the spiraling air
 flow or disrupting it so much it might not meet the specs of a smaller round probe designed for it. I would think at the least it might be the thing to do to remove the big davis filter in favor of the smaller low profile of the sf1.

[Bobvelle]

So I'm confused. The 7714 passive shield plates come out of the box, black on the underside ? Or you had to paint them?

I painted mine  Flat Black just bottom plate where sensor mounts  and the nearest top plate toward sensor. I used painters blue tape edges around upper plate so only white (no black) was exposed to sun. Instructions on assembly can be tricky. Better to assembly first time then once you figure that out you will understand what parts I painted black.

Oh OK..So it was the Metoeshield that comes black on the underside. I got them confused.
I just looked at the Meteoshield specs and It's a lot smaller than the Davis shields as far as diameter. Inside diameter is ~ 2.56". But if you could mount the SHTxx PCB vertically (as in the cable hanging straight down) you should have ~.5" on either side which would allow you to place the PCB off-center. thereby positioning the sensor about center. This would allow an upward draft through the center with only the Davis filter cap (assuming you use it) in the airflow.  However, horizontal airflow would be blocked. But according to the design intent, and unlike most gill plate shields.. natural aspiration should be a "quasi-spiral-vertical" (Helical) movement, should it not?

I was in contact with Jan at Metoshield about the big stock filter, he thought it would work. Until I get the shield and see not totally convinced so ordered some of the small filters just in case.

Well I think there is room... but then the bigger question is... how and what would you mount it to? There are no mounting brackets up inside the interior that I'm aware of. Looking at the PDFs, the only "bracket" for mounting a sensor is the 1/2" or 3/4" hole in the bottom plate for what looks like a "seal-tite" elec. box connector. Some kind of home-brew bracket/mount would have to be found by sorting through the 30+ years of junk I have stashed here and there. But, after all, isn't that the fun of it. 

[ValentineWeather]

I was wondering the same thing about the big sensor blocking the spiraling air
 flow or disrupting it so much it might not meet the specs of a smaller round probe designed for it. I would think at the least it might be the thing to do to remove the big davis filter in favor of the smaller low profile of the sf1.

I thought the 31's took the SF2's You sent me a link. That's what I ordered. So do I have the wrong filter coming?

Sensirion says its the SF2.    SF2 Filter Cap
For SHT2x and SHT3x Humidity Sensors

https://www.sensirion.com/en/environmental-sensors/humidity-sensors/filter-cap-sf2/

[dendrite]

I was wondering the same thing about the big sensor blocking the spiraling air
 flow or disrupting it so much it might not meet the specs of a smaller round probe designed for it. I would think at the least it might be the thing to do to remove the big davis filter in favor of the smaller low profile of the sf1.

I thought the 31's took the SF2's You sent me a link. That's what I ordered. So do I have the wrong filter coming?

Sensirion says its the SF2.    SF2 Filter Cap
For SHT2x and SHT3x Humidity Sensors

https://www.sensirion.com/en/environmental-sensors/humidity-sensors/filter-cap-sf2/

I think you’re fine. I believe the SF1 was for the SHT1x.

[openvista]

Here is some interesting research on radiation shields...

https://journals.ametsoc.org/doi/pdf/10.1175/1520-0426(2001)018%3C0851%3ATEOTAM%3E2.0.CO%3B2

Summary:

ASOS > CRS > MMTS > Gill = rank of solar radiation shield effectiveness.
CRS > MMTS > Gill > ASOS = DAYTIME rank of infrared radiation shielding effectiveness.
Gill ≥ MMTS > CRS ≈ ASOS = NITETIME rank of infrared radiation shielding effectiveness.

...where:

ASOS = Automated Surface Observing System shield
MMTS = Maximum-Minimum Temperature System shield
CRS = Cotton Region (Stevenson) Shelter.
Gill = multliple-plate cylindrical shaped shield

That's the old ASOS shield (circa 2000) that had the chilled mirror in it. They had to leave the bottom open which really messed it up with ground reflected radiation, especially at night. They discuss this in the abstract and then again around pp 861-863 in the paper.

The newer ASOS's have a separate housing for dew point. Not sure, but I doubt, the aspirated temperature shield is still left open at the bottom now. Ron would have to verify.

[ValentineWeather]

I was wondering the same thing about the big sensor blocking the spiraling air
 flow or disrupting it so much it might not meet the specs of a smaller round probe designed for it. I would think at the least it might be the thing to do to remove the big davis filter in favor of the smaller low profile of the sf1.

I thought the 31's took the SF2's You sent me a link. That's what I ordered. So do I have the wrong filter coming?

Sensirion says its the SF2.    SF2 Filter Cap
For SHT2x and SHT3x Humidity Sensors

https://www.sensirion.com/en/environmental-sensors/humidity-sensors/filter-cap-sf2/

I think you’re fine. I believe the SF1 was for the SHT1x.

Could be the SF1 has to be larger, maybe that's what he likes it for better handling and gluing down. Can't image any sensor smaller than the tiny 31's so about any filter should fit.

[CW7491]

Here is some interesting research on radiation shields...

https://journals.ametsoc.org/doi/pdf/10.1175/1520-0426(2001)018%3C0851%3ATEOTAM%3E2.0.CO%3B2

Summary:

ASOS > CRS > MMTS > Gill = rank of solar radiation shield effectiveness.
CRS > MMTS > Gill > ASOS = DAYTIME rank of infrared radiation shielding effectiveness.
Gill ≥ MMTS > CRS ≈ ASOS = NITETIME rank of infrared radiation shielding effectiveness.

...where:

ASOS = Automated Surface Observing System shield
MMTS = Maximum-Minimum Temperature System shield
CRS = Cotton Region (Stevenson) Shelter.
Gill = multliple-plate cylindrical shaped shield

That's the old ASOS shield (circa 2000) that had the chilled mirror in it. They had to leave the bottom open which really messed it up with ground reflected radiation, especially at night. They discuss this in the abstract and then again around pp 861-863 in the paper.

The newer ASOS's have a separate housing for dew point. Not sure, but I doubt, the aspirated temperature shield is still left open at the bottom now. Ron would have to verify.

I was surprised when I saw for myself the ASOS HO-1088 is still open at the bottom with the temperature sensor nearly all the way at the bottom. The only thing between the sensor and the ground is a screen. And I’m not certain, but I don’t even think they’ve removed the chilled mirror device; they just don’t use it. 

[Bobvelle]

I was wondering the same thing about the big sensor blocking the spiraling air
 flow or disrupting it so much it might not meet the specs of a smaller round probe designed for it. I would think at the least it might be the thing to do to remove the big davis filter in favor of the smaller low profile of the sf1.

I thought the 31's took the SF2's You sent me a link. That's what I ordered. So do I have the wrong filter coming?

Sensirion says its the SF2.    SF2 Filter Cap
For SHT2x and SHT3x Humidity Sensors

https://www.sensirion.com/en/environmental-sensors/humidity-sensors/filter-cap-sf2/

I think you’re fine. I believe the SF1 was for the SHT1x.

Could be the SF1 has to be larger, maybe that's what he likes it for better handling and gluing down. Can't image any sensor smaller than the tiny 31's so about any filter should fit.

SF2 is for the SHT3x
SF1 is for the SHT1x

SF2 is just an open box underneath that covers the whole sensor. It leaves a airspace all the way around the sensor.
SF1 has a tunnel like opening that is offset to only allow the actual sensor orifice of the SHT11 or 15 exposed to the membrane. It's designed specifically for the SH1x series sensor and AFAIK will not fit any other sensor.

[ValentineWeather]

Thanks so have the right one coming.

[ValentineWeather]

Day 3, summary passive shield 7714 (+1.2°F) over FARS on high temperature. Mostly sunny just few clouds temperatures 70's, winds up just a little (1-9 mph) with passing of weak cold front. Wind measured at 30'.
Expect mid 90's tomorrow will be warmest test day.
Acceptable.
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[ValentineWeather]

Only .3F difference day 4 mid 90's with wind passive and fars are the same.
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[CW2274]

With that wind, should be close. When conditions are ripe, show us, as we used to say, a "dac" day.

[ValentineWeather]

The 7714 is best passive shield I've tested so far.
But the shield I'm really looking forward to is the meteoshield.  This was my baby giving Jan the idea of fitting Davis sensor inside so really hope it performs.

[jerryg]

Ok this is just a quick update got the two shields in awhile ago and just put out the pro, wanted to try it at noon in the heat of the day and little to no wind right now and the fars is showing 90.6 and the pro 90.1 first quick look and the standard shield has plenty of room for the davis sensor it can be wiggled around inside. Will give up date later when get some good looks at the pro.

[jerryg]

Just had a thought if i remember right i think that a passive shield is supposed to run cooler at night than a fars. It will be another thing i check out tonight to see how much if any temp difference there is.

[jgentry]

Just had a thought if i remember right i think that a passive shield is supposed to run cooler at night than a fars. It will be another thing i check out tonight to see how much if any temp difference there is.

How is the FARS and the Barani shield comparing now?

[ValentineWeather]

Barani shields are still in customs, takes about a week maybe getting close now. Once retailer receives they get shipped to customers.

Jerry I don't find high noon the time of day for passive shields showing most error, this usually starts around 4pm and ends around 6:30 pm this time of year.

[jerryg]

Maybe so i am sitting here looking at the two stations and i can not figure out why the fars is running on average a degree higher. I was concerned about temp spike of the pro and now i wonder about the fars. I moved the shield between the two fars and nothing changed and i moved the sensor inside the fars between the two fars and same thing. The difference is always the same no matter the combo. One thing the mounting for the Barani shield is sort of universal mounts with screws  or u bolts the ones from Davis mount fit fine. Tomorrow i am going to get the standard shield set up with a 31 sensor.

[dendrite]

So which sensors are in which shields? Pretty crazy the FARS is running warmer. What are you using for a fan in the FARS? I have 40 CFM going through so way more than the Davis stock.

[jerryg]

I have an sht 75 in my main station and i just set out the standard shield with a Davis sht 31 and my fars is also an sht 31. All the sensors were compared in temp to each other and were always within a .1 to .2 of each other. I made a mount for the standard shield that works pretty well, nothing fancy but the unit comes with a cable clamp fitting that i put a 6 inch piece of tubing into that is 1 inch outside diameter and just fits and lets me slide it up and down to position the sensor in a good spot and then tighten it down to secure it. The two Barani shields are running pretty close to each other in temp. That's a good sign for Davis sensor users. Will know more after watching it for awhile, really waiting for tonight to see how the humidity pans out.

[ValentineWeather]

Okay after reading all the threads looks like this will turn into a Barani shield test thread also. I'll add the name to title.

[ValentineWeather]

Yes good sign if Fars is running higher unless Jerry has modified Davis shield causing it to run warmer, like I did with open bottom (Don't do this), 

[jerryg]

No mods just Davis fars with stock fans.

[Bobvelle]

Barani shields are still in customs, takes about a week maybe getting close now. Once retailer receives they get shipped to customers.

OK... Barani...Meteoshield...Standard shield  Are we all talking about the same thing here?

And If so, Doesn't Jerryg and Jgentry already have the Meteoshields? How are they held up in Customs...???