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

[jgentry]

I have had my modified 75 in a  Meteoshield Pro for several days now with the stock Davis filter.  Here is my station dw5686 if you want to follow along with my stats compared to MADIS and two ASOS stations one 5 miles east (CLT) and the other 8miles southwest (AKH). I also upload to WxUnderground if you want to follow my data more in real time.

https://weather.gladstonefamily.net/site/D5686
https://www.wunderground.com/personal-weather-station/dashboard?ID=KNCBELMO18#history

So far I'm very happy as it seems my CWOP stats haven't changed very much at all. Perhaps running just .2F to .3F warmer compared to other stations than I used to. When comparing highs and lows I to local ASOS I go back and look at my one minute data and find the 5min running avg for the high and low for the day.  I think this is important that you do this since when comparing your readings with ASOS as it smooths out temperature data this way.  Anyhow, I have been running either even or one degree cooler than my local ASOS stations which is on par when I was running a davis FARS with stock fan, actually the replacement 3V motor from Nichibo.

Weather has been great for testing except for cloud cover.  Hot humid afternoons with light winds, but with scattered to broken layers. Want to eventually get around to some side by side testing with my FARS but from what jerryg has found in his testing it sounds like both the meteoshields and especially the pro may be promising alternatives to aspirated shields.

Very nice so another with a pro.

Has me thinking do I want to change at least 1 shield coming to a pro?

As of now, that’s what I’m planning on doing. For me, it will help the humidity sensor and will not have to worry about all the maintenance stuff. From what I understand so far, as long as you get a little breeze during the daytime hours, you’re in good shape.

[ValentineWeather]

Can't find the Krylon fusion black silk but did find camo version may actually be better called ultra flat in dark brown.
Process of smell test now after drying with hair dryer.
Left is the Krylon fusion Ultra flat camo. These are the 1/2" conduit PVC standpipes I'll use for mounting the 31's inside the meteoshield standard.

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[jerryg]

Just a quickie, i got a 31 to fit inside the pro, tight, but it will go when you whack off the excess board on the right side of the sensor.

[ValentineWeather]

Just a quickie, i got a 31 to fit inside the pro, tight, but it will go when you whack off the excess board on the right side of the sensor.

Very nice now what do I do?  LOL

[jerryg]

I did not leave it in too long to see if the size caused any air flow problems was just for fit. I had the shield up and down a few times today trying stuff and just got it back on for good i hope. i fixed up my sensor board so that i can slide the tube out with the sensor attached so i don't have to take the base apart. Now i can adjust the sensor height but remove it to try a different one easily. So at 2:20 pro 89.8 and standard 90.0 wind 6 to 10 mph and partly cloudy.  Need to add the sky is cloudy right now so temps are closer than they would be if in sunshine.

[jerryg]

3 pm still cloudy pro 91.1 standard 913 forgot to add wind 5-12 mph

[jerryg]

Update 4pm pro 91.0 standard 91.0 still cloudy and windy 12 to 16 mph

[jerryg]

Update 5pm pro 92.8 std 93.1 sunny winds 7-10 mph

[jerryg]

Update 6pm pro 91.0 standard 91.2 partly cloudy wind 5 to 12 mph

[ValentineWeather]

Thanks for updates Jerry. Any chance of a day when winds are near calm?

[jerryg]

Where i live it's not if the wind will blow but how high will the winds get lol. No more updates today this time of day they pretty much match each other without the sun influence nearly all shields are great lol.

[ValentineWeather]

Here is todays test with passive 7714 vs fars. Sunny, wind speeds up just a little around 3-5 mph peak gust was 16 mph.
Both FARS and 7714 recorded exact 86.3° high.

It's clear the 7714 is a great little shield. Doesn't take much wind and performs just as well.
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[CW2274]

It's clear the 7714 is a great little shield. Doesn't take much wind and performs just as well.

No doubt that it's really good, but the thing is, if passive shields were that good, fans would have never been used in the first place.
It'll be a cold day in H E double hockey sticks before you see an ASOS with a passive shield.

[jerryg]

That's true but it depends on how good your fars is doing, some are better than others. Just having a fan doesn't mean you have the best. Like i said davis compares theirs to the rm young and says withing .6 and rm specs out at .4 so davis could be 1 degree higher than air temp. Now i was wondering if rm young tests their shield over grass low wind at solar noon what are they using as a reference for the actual air temp, how is it measured at the test site to know what the air temp is at any given time. If they have a super accurate temp sensor what do they put it in to get the actual air temp? I want the perfect shield they use for calibration lol.

[CW2274]

That's true but it depends on how good your fars is doing, some are better than others. Just having a fan doesn't mean you have the best.

Of course! All I'm saying is that fans aren't going anywhere in high end measurements.
I would love to see the pro shield compare to my properly aspirated 24hr VP2 when the wind is >5 mph and temps in the 105F+. It could be fantastic, but it would have to be revolutionary (and it's obvious they're pitching exactly this) for me to even think of giving up my fan.

[hwcorder]

It's clear the 7714 is a great little shield. Doesn't take much wind and performs just as well.

No doubt that it's really good, but the thing is, if passive shields were that good, fans would have never been used in the first place.
It'll be a cold day in H E double hockey sticks before you see an ASOS with a passive shield.

Passive shields have come a long way and with more and more automated stations going in remote locations the need for low maintenance equipment will require the technology to progress.  With that being said my old cotton region shelter was pretty good back in the day and that design has been around for ages.

Anyway, my high for the day in the Meteoshield Pro was 94F.  AKH to my west hit 93 and CLT to my east 92.  CLT seemed to sit at 91-92 for several hours this afternoon which was a little odd, possibly from a little more cloud cover than my location.  Will see what happens tomorrow as weather should be very similar to today.

The high did occur when winds became light or nearly calm so this could have been from a little solar heating. Like others I wonder if the big davis filter interrupts airflow within the sensor. chamber  I am actually working on converting an ink pin into a temp/hum probe using my 75 that will fit in the bottom opening.  Ordered a few different filter caps from Campbell Scientific and found one that works very well.  Just need to mount the wiring then weatherproof the connections.   

[ValentineWeather]

Something just came up from hwcorder post about using stock filter on modified 73. How about others?  I don't see a specifically made filter for these so do they even require a filter?  if so is it just some homebrew like wrapping sensor in davis type filter material?   

[dendrite]

Something just came up from hwcorder post about using stock filter on modified 73. How about others?  I don't see a specifically made filter for these so do they even require a filter?  if so is it just some homebrew like wrapping sensor in davis type filter material?

The Campbell Sci tem/hum probe uses the 75.

https://www.campbellsci.com/cs215-l (click "read more")


I'd assume that probe filter housing is available somewhere in accessories or replacement parts.

[dendrite]

Heh...found this in the CS215-L manual. I assume this applies to all Sensirion sensors...

Measurement Below 0 °C
The CS215 provides a humidity reading that is referenced to the saturated water vapor pressure above liquid water, even at temperatures below 0 °C, where ice might form. This is the common way to express relative humidity and is as defined by the World Meteorological Organization. If an RH value is required to be referenced to ice, the CS215 readings will need to be corrected.
One consequence of using water as the reference is that the maximum humidity that will normally be output by the sensor for temperatures below freezing is as follows:
100% RH at 0 °C
95% RH at –5 °C
91% RH at –10 °C
87% RH at –15 °C
82% RH at –20 °C
78% RH at –25 °C
75% RH at –30 °C
In practical terms this means that, for instance, at –20 °C the air is effectively fully saturated when the sensor outputs 82% RH.

[ValentineWeather]

Something just came up from hwcorder post about using stock filter on modified 73. How about others?  I don't see a specifically made filter for these so do they even require a filter?  if so is it just some homebrew like wrapping sensor in davis type filter material?

The Campbell Sci tem/hum probe uses the 75.

https://www.campbellsci.com/cs215-l (click "read more")


I'd assume that probe filter housing is available somewhere in accessories or replacement parts.

The filter cap they use is https://www.campbellsci.com/p18142 and you request a quote. surely this isn't what most use is it? When they say request a quote it's beyond my price...

[ValentineWeather]

Found these https://www.aliexpress.com/item/2pcs-Waterproof-Temperature-and-humidity-sensor-shell-SHT10-SHT21-SHT15-shT11-sht20-SHT75-sensor-protective-sleeve/32725766858.html?spm=2114.search0104.3.16.7f3c5891DPRtm1&ws_ab_test=searchweb0_0,searchweb201602_1_10152_10151_10065_10344_10068_10130_10324_10342_10547_10325_10343_10546_10340_10548_10341_315_10545_10696_10084_531_10083_5011611_10618_10307_5011511_5723611_10059_100031_10103_10624_10623_10622_10621_10620,searchweb201603_6,ppcSwitch_5&algo_expid=125061b9-f6a7-4d33-be9e-ed1a5566bfc1-2&algo_pvid=125061b9-f6a7-4d33-be9e-ed1a5566bfc1&priceBeautifyAB=0

These guys have a custom mount. https://www.emesystems.com/sht75pg/main.html

[ValentineWeather]

Waiting for more ideas. In meantime why can't we just use the existing Davis material, use cotton thread and tie material around the SHT75 sensor. Don't know why it wouldn't work. 

[jerryg]

Looks pretty good so i order some, hope they are as shown lol.

[ValentineWeather]

Looks pretty good so i order some, hope they are as shown lol.

Same here, used paypal. I heard they are trustworthy, some people buy cameras all the time.
19-39 days is a wait however.

[jerryg]

Well waiting is what we do a lot of messing with this stuff, try something new then wait with fingers crossed lol. It will be neat if the filter end could be fastened to the tube and cover the 75. Would make a nice probe. I am just trying to decide if i want to put the 31 in the pro and see how it performs, i removed the little sliver of board next to where the cable is, every little bit helps it to fit. So now all the excess board is removed right next to the stuff davis covers the board with. It doesn't take too long to change it, just hate messing with those little 7 mm nuts, my fingers just refuse to hold them secure, slippery little devils lol. It would be nice to know how it shapes out with the 75 being phased out.