Author Topic: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD  (Read 17073 times)

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Offline jerryg

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #375 on: August 16, 2018, 06:18:10 PM »
I'm sure at any given time the readings can be one way or the other that is why the most important reading to me is the min/max of the day so all the up and downs of the day can be ignored as far as i am concerned.

Offline dendrite

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #376 on: August 16, 2018, 06:21:05 PM »
Just as a further thought, this is exactly why ASOS's use an averaging algorithm, to eliminate the high and low spikes that we aspirated PWS folks take for granted.
I think the 5-min running averages best mimicked Hg thermometers. So when these stations went from max/min liquid-filled thermometers to aspirated probes they needed the averaging to maintain consistency with the climo record.

Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #377 on: August 16, 2018, 06:30:51 PM »
I'm sure all of us have seen our temp go up a degree or whatever for a packet cycle, then never to be seen again, that's our high. An ASOS would never report such a thing as valid, only as a number to be averaged in it's determined cycle.

Offline dendrite

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #378 on: August 16, 2018, 06:41:45 PM »
I'm sure all of us have seen our temp go up a degree or whatever for a packet cycle, then never to be seen again, that's our high. An ASOS would never report such a thing as valid, only as a number to be averaged in it's determined cycle.
Good stuff here...

https://training.weather.gov/nwstc/DATAACQ/d.ASOShuman/Temp.htm

Offline jerryg

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #379 on: August 16, 2018, 06:45:33 PM »
I am sure that for official records and stuff that some kind of averaging is needed but for us pws owners and our fans  :lol: most asked what was the high or low temp for the day, not caring about averages etc. Most people don't care about the little up and downs of the day.

Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #380 on: August 16, 2018, 07:09:07 PM »
I'm sure all of us have seen our temp go up a degree or whatever for a packet cycle, then never to be seen again, that's our high. An ASOS would never report such a thing as valid, only as a number to be averaged in it's determined cycle.
Good stuff here...

https://training.weather.gov/nwstc/DATAACQ/d.ASOShuman/Temp.htm
Indeed, read the whole thing. I certainly remember the HO-83 fiasco here in the early nineties, even the Chamber of Commerce got involved.
Makes me love my well aspirated PWS even more.

Offline hwcorder

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #381 on: August 16, 2018, 07:24:44 PM »
I'm sure all of us have seen our temp go up a degree or whatever for a packet cycle, then never to be seen again, that's our high. An ASOS would never report such a thing as valid, only as a number to be averaged in it's determined cycle.
Good stuff here...

https://training.weather.gov/nwstc/DATAACQ/d.ASOShuman/Temp.htm
Indeed, read the whole thing. I certainly remember the HO-83 fiasco here in the early nineties, even the Chamber of Commerce got involved.
Makes me love my well aspirated PWS even more.

If I remember correctly it wasnt due to lack of aspiration the problem more associated with exhaust air being recirculated back through the HO-83.  Air being deflected down from the top rounded dome at the top of the shield was then getting sucked back into the intake at the bottom.  Every time this happened the air was warmed little by little.  This is why they added the fin towards the bottom of the shield to deflect air to the side preventing recirculation.
« Last Edit: August 16, 2018, 07:28:09 PM by hwcorder »

Offline Bobvelle

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #382 on: August 16, 2018, 07:31:48 PM »
If you are asking me yes the fars is a stock davis set up other than i am running the fan off of a walwart at 2.3 volts during the day and 1 volt at night using a photocell and relay setup.

What are you using after the relay switches to reduce the voltage? I tried doing this with a 20ohm resistor but that resistor was getting way too hot. Trying to find something I have laying around instead having to buy a voltage regulator.

Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #383 on: August 16, 2018, 07:39:33 PM »
I'm sure all of us have seen our temp go up a degree or whatever for a packet cycle, then never to be seen again, that's our high. An ASOS would never report such a thing as valid, only as a number to be averaged in it's determined cycle.
Good stuff here...

https://training.weather.gov/nwstc/DATAACQ/d.ASOShuman/Temp.htm
Indeed, read the whole thing. I certainly remember the HO-83 fiasco here in the early nineties, even the Chamber of Commerce got involved.
Makes me love my well aspirated PWS even more.

If I remember correctly it wasnt due to lack of aspiration the problem more associated with exhaust air being recirculated back through the HO-83.  Air being deflected down from the top rounded dome at the top of the shield was then getting sucked back into the intake at the bottom.  Every time this happened the air was warmed little by little.  This is why they added the fin towards the bottom of the shield to deflect air to the side preventing recirculation.
Took me awhile to find...here ya go.
https://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281992%29005%3C0657%3ATRMTAI%3E2.0.CO%3B2

Offline openvista

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #384 on: August 16, 2018, 07:43:13 PM »
The WMO study came to the opposite conclusion of every other shield comparison I've ever read (and I've read plenty of 'em). Therefore, many more studies finding aspirated shields are "disappointing" compared to passive shields in high insolation, low wind situations are necessary before I'd buy in.

But that won't keep me from running as honest a test as I can between the 7714 and FARS.

Seems to me that it would be well enough to find a passive shield running even with the FARS, which is, apparently, what we are seeing with the Meteoshield Pro and to a lesser extent, the 7714. 

Tomorrow I get Randy's weather and will put the 7714 through its paces.
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Offline Bobvelle

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #385 on: August 16, 2018, 07:43:28 PM »
So here is today after making the changes to even out exposure. Pretty much the same thing. +2 deg avg. afternoon sun with the Meteo Standard..

SHT31 Meteoshield standard
SHT31 Davis FARS

Afternoon Wind ~1.5 mph

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Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #386 on: August 16, 2018, 07:45:38 PM »
If you are asking me yes the fars is a stock davis set up other than i am running the fan off of a walwart at 2.3 volts during the day and 1 volt at night using a photocell and relay setup.

What are you using after the relay switches to reduce the voltage?
Just me, but I still think this is a complete waste of time. Let'er rip.

Offline ValentineWeather

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #387 on: August 16, 2018, 07:45:51 PM »
Well great test day with wind speed very low 0 mph much of day, sunny except maybe 2 clouds all day.

This is what can be expected on worse day passive vs FARS.
Both Meteoshields have additional top shield. I'm little skeptical of how well it helps at this latitude but it did provide partial shade most of day. That of course ends as we go into winter and top cover does little shading. As stated several times the Meteoshields have good response for passive they really leave the 7714 in the dust.
 
I can't recommend the Standard even at price point. Not horrible but I would spend money on the better 7714 before the standard.

The PRO is better than the 7714 imo so plan on adding second unit if they take the standard shield back. Still no response from them on returning. Maybe they didn't like what I said about it.  Just it didn't meet my expectations...What's wrong with that? :lol:

Anyone getting one of these shields I recommend the 30' sensor just because the Davis plugs are so short. I do think Jerry said he got one working with stock setup but not 100% on that. 
You will need to cut down the sensor to fit inside the Pro shield. I just used tin snips. For filter I used low VOC glue and just glued on using one corner of Davis filter. The glue I used easily pulls off later for changing. One stock Davis filter gives 4 filter changes.
 
Broke down FARS against each shield for cleaner comparision

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« Last Edit: August 16, 2018, 08:36:16 PM by ValentineWeather »
Randy

Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #388 on: August 16, 2018, 08:00:25 PM »
Therefore, many more studies finding aspirated shields are "disappointing" compared to passive shields in high insolation, low wind situations are necessary before I'd buy in.
+1   There's not enough convoluted evidence on this planet that could convince me that a passive shield would out perform an aspirated shield in my climate when your skin will burn in literal minutes and the wind is calm.

Offline CW2274

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #389 on: August 16, 2018, 08:04:56 PM »
Well great test day with wind speed very low 0 mph much of day, sunny except maybe 2 clouds all day.

This is what can be expected on worse day passive vs FARS.
Both Meteoshields have additional top shield. I'm little skeptical of how well it helps at this latitude but it did provide partial shade most of day. That of course ends as we go into winter and top cover does little shading. As stated several times the Meteoshields have good response for fars they really leave the 7714 in the dust.
 
I can't recommend the Standard even at price point. Not horrible but I would spend money on the better 7714 before the standard.

The PRO is better than the 7714 imo so plan on adding second unit if they take the standard shield back. Still no response from them on returning. Maybe they didn't like what I said about it.  Just it didn't meet my expectations...What's wrong with that? :lol:

Anyone getting one of these shields I recommend the 30' sensor just because the Davis plugs are so short. I do think Jerry said he got one working with stock setup but not 100% on that. 
You will need to cut down the sensor to fit inside the Pro shield. I just used tin snips. For filter I used low VOC glue and just glued on using one corner of Davis filter. The glue I used easily pulls off later for changing. One stock Davis filter gives 4 filter changes.
 
Broke down FARS against each shield for cleaner comparision

As always Randy.... =D>

Offline openvista

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #390 on: August 16, 2018, 08:08:10 PM »
By the way, I have an idea for a pole mounting solution for the VP2 SIM (removing it from the rain base completely) if anyone needs it.

I'm going to take a piece of 12" x 12" x 0.5" acrylic (https://www.amazon.com/gp/product/B00C13Z6UI/ref=od_aui_detailpages00?ie=UTF8&psc=1), cut it to size and route out a hole for the clip so it rests flush.

Then drill a hole in the upper right and lower left of the housing, thread through a couple 1/4" bolts with washers and lock nuts on other side.

Because the clip on the rear is 3/4" deep and the acrylic is only 1/2" thick, you can't mount the u-bolt above the SIM and or clip will go through the hole, hitting the pole and preventing the SIM from sitting flush against the acrylic. So I plan to mount the u-bolt beside the SIM (which is 5" wide, 6.5" long). 3/4" thick acrylic was more than 3x the price!

Also, there are a couple 1/4" deep bump outs on the right side that can be balanced with an extra nut and washer on the left side (between the SIM and acrylic) or a proper 1/4" standoff if you have one.

I thought about using a J-bolt against the clip, but then you could only balance that with one bolt in the upper right (and a 3/4" standoff). The left side would just hang there because there's not enough space in the upper left or center top for a bolt. The wind could flex it over time and weaken the plastic around the other bolts.
« Last Edit: August 16, 2018, 08:13:51 PM by openvista »
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Offline openvista

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #391 on: August 16, 2018, 08:13:12 PM »
Well great test day with wind speed very low 0 mph much of day, sunny except maybe 2 clouds all day.

This is what can be expected on worse day passive vs FARS.
Both Meteoshields have additional top shield. I'm little skeptical of how well it helps at this latitude but it did provide partial shade most of day. That of course ends as we go into winter and top cover does little shading. As stated several times the Meteoshields have good response for fars they really leave the 7714 in the dust.
 
I can't recommend the Standard even at price point. Not horrible but I would spend money on the better 7714 before the standard.

The PRO is better than the 7714 imo so plan on adding second unit if they take the standard shield back. Still no response from them on returning. Maybe they didn't like what I said about it.  Just it didn't meet my expectations...What's wrong with that? :lol:

Anyone getting one of these shields I recommend the 30' sensor just because the Davis plugs are so short. I do think Jerry said he got one working with stock setup but not 100% on that. 
You will need to cut down the sensor to fit inside the Pro shield. I just used tin snips. For filter I used low VOC glue and just glued on using one corner of Davis filter. The glue I used easily pulls off later for changing. One stock Davis filter gives 4 filter changes.
 
Broke down FARS against each shield for cleaner comparision

As always Randy.... =D>

Yes, Randy, thank you for the data!
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Offline jerryg

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #392 on: August 16, 2018, 08:18:34 PM »
I to tried resistors but way too much variations in voltage so i just used the drop across a silcon diode at .7 volts. I had a 3 volt wallwart and put 3 diode in series which gave me a volt for night time use and the relay at night is basically not in use then in the am the photocell pulls the relay closed and i use a set of normal open contacts that close when the relay pulls and shorts out 2 of the diodes of the 3 that are in series which gives me just one diode for a voltage of 2.3 volts for daytime running.

Offline jerryg

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #393 on: August 16, 2018, 08:26:18 PM »
I think everyone needs to remember that the location that i am at is great for the pro and some locations like the desert southwest may need the fars. In my location wind is not a problem, it blows most of the time and i don't have extreme heat or cold and my main concern is the high humidity at night that we have nearly year round and the effect it has on the Davis sensors. Everything is a trade off of some kind, i would think in the hot s.w. region that the more air the better. I am fortunate that mother nature supplies me with an abundance of moving air lol.













Offline Bobvelle

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #394 on: August 16, 2018, 08:54:47 PM »
I to tried resistors but way too much variations in voltage so i just used the drop across a silcon diode at .7 volts. I had a 3 volt wallwart and put 3 diode in series which gave me a volt for night time use and the relay at night is basically not in use then in the am the photocell pulls the relay closed and i use a set of normal open contacts that close when the relay pulls and shorts out 2 of the diodes of the 3 that are in series which gives me just one diode for a voltage of 2.3 volts for daytime running.

HA! that's genius Jerry  :grin:
Didn't even think of that.

I was only considering it when someone mentioned (maybe you) pulling in a full volume of air at night was likely adding unnecessary moisture to the interior of the FARS causing higher than usual RH readings during the day.  Of course, If this is not the case, than I will forego that experiment and leave it as is. Very Humid and Very little air here.

Offline Bobvelle

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #395 on: August 16, 2018, 09:06:55 PM »



 
Broke down FARS against each shield for cleaner comparision


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Great Info!
Are the temps at the top the Average or standard deviation or...?
It Looks like my standard Meteo is doing about as good as your Pro...I'm only getting 1.5 -2 deg difference in the sun too Hmm

Offline ValentineWeather

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #396 on: August 16, 2018, 10:05:15 PM »



 
Broke down FARS against each shield for cleaner comparision


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Great Info!
Are the temps at the top the Average or standard deviation or...?
It Looks like my standard Meteo is doing about as good as your Pro...I'm only getting 1.5 -2 deg difference in the sun too Hmm

No should have been clear those are peak max differentials, may only happened once but when you report highs and lows that’s all they look at.
Randy

Offline dendrite

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #397 on: August 16, 2018, 10:17:46 PM »
i don't have extreme heat
heh. I think 99% of the forum had to laugh at that one. ;)

Offline openvista

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #398 on: August 16, 2018, 10:44:27 PM »



 
Broke down FARS against each shield for cleaner comparision


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Great Info!
Are the temps at the top the Average or standard deviation or...?
It Looks like my standard Meteo is doing about as good as your Pro...I'm only getting 1.5 -2 deg difference in the sun too Hmm

Well, what's your wind like? Looks like Randy hit a max of 2mph the entire test period today! That's about as good as it gets for testing shields. If there were any errors to be found, they'd be sure to show up.

EDIT: missed that you posted 1.5mph avg wind. Randy didn’t give an average but his appears to be lower just looking at his graph. That might explain the discrepancy.
« Last Edit: August 17, 2018, 02:23:29 AM by openvista »
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Offline Old Tele man

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Re: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD
« Reply #399 on: August 16, 2018, 11:26:09 PM »
In WEATHER as in REAL ESTATE, it's all about LOCATION, LOCATION, LOCATION ( :roll: )!
• SYS: Davis VP2 Vue/WL-IP & Envoy8X/WL-USB;
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• CWOP: DW6988 - 2 miles NNE of Cortaro, AZ
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anything