Author Topic: Field study thermometer shields FARS 7755, Passive 7714, & new METEOSHIELD  (Read 8176 times)

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Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #50 on: July 28, 2018, 10:54:39 AM »
I see more now flat black on inside, even the single probe gill shields.  I think it came from a study WMO did some years back showing the benefit. They even tested Stevenson screens with white and black interiors. Black always had less error because the flat black reduces heat reflection by absorbing it, I believe was how it was explained.   
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Online jerryg

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #51 on: July 28, 2018, 11:14:45 AM »
It just seems to me to make good sense that you would want to reflect all the solar energy you could be fore it gets inside and absorb all you could before it gets to the sensor instead of having it white inside and bouncing all that heat around in the chamber.

Offline Old Tele man

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #52 on: July 28, 2018, 12:58:03 PM »
The insides of ALL optical devices (cameras, binoculars, telescopes, etc.) are painted flat black to absorb and de-scatter stray light, which includes long wavelength infrared where the heat is.

The protocol for ALL optical and thermal sensing devices used at USArmy Yuma Proving Ground is shiny WHITE/top surfaces with flat BLACK/bottom surfaces.

That's how my solar shields are now, however, there IS a caveat, not all white paints are 100% reflective and not all black paints are 100% absorptive...AND, some paints want to dissolve/eat the plastic plates (depends on the plastic). For now, I'm using Rustoleum Flat Black and Gloss White...but I'm interested to hear what others use.
« Last Edit: July 28, 2018, 01:24:26 PM by Old Tele man »
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Online jerryg

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #53 on: July 28, 2018, 01:11:50 PM »
I haven't played with black yet but i used  Rust. flat white paint made for plastic and uv resistant. I am not sure how you tell if black will be absorbent or not, just thought black would absorb being black and all lol. Need a paint guru to chime in here. :???:

Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #54 on: July 28, 2018, 01:27:34 PM »
I'm starting this test over today because the first day shield being used was modified with bottom removed so I could insert another sensor inside.

I believe this was allowing reflective heat waves inside sensor chamber causing a slight warming. I went back to stock shield with AC fan today. I'm currently seeing FARS running .3 to .5 F cooler with completely stock shield. Still not bad for passive but will need to continue testing.
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« Last Edit: July 28, 2018, 01:33:42 PM by ValentineWeather »
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Offline SnowHiker

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #55 on: July 28, 2018, 02:44:18 PM »
I haven't played with black yet but i used  Rust. flat white paint made for plastic and uv resistant. I am not sure how you tell if black will be absorbent or not, just thought black would absorb being black and all lol. Need a paint guru to chime in here. :???:
Not a paint guru, so I'll just state what's probably more or less obvious.  If you paint the inside of your shield you better give the paint plenty of time to dry before putting the sensor in, as there seems to already be a lot of concern about contamination.  Also I would be a little concerned about the paint, especially if low quality, eventually flaking and turning to dust, even though not in direct sunlight, possibly causing more problems.

Offline Old Tele man

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #56 on: July 28, 2018, 02:55:07 PM »
I haven't played with black yet but i used  Rust. flat white paint made for plastic and uv resistant. I am not sure how you tell if black will be absorbent or not, just thought black would absorb being black and all lol. Need a paint guru to chime in here. :???:
Not a paint guru, so I'll just state what's probably more or less obvious.  If you paint the inside of your shield you better give the paint plenty of time to dry before putting the sensor in, as there seems to already be a lot of concern about contamination.  Also I would be a little concerned about the paint, especially if low quality, eventually flaking and turning to dust, even though not in direct sunlight, possibly causing more problems.
Absolutely, 'out-gassing' of paint volatile's will detrimentally affect RH sensor accuracy.
« Last Edit: July 28, 2018, 03:44:09 PM by Old Tele man »
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Offline kcidwx

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #57 on: July 28, 2018, 03:03:29 PM »
Yes, they do. I've worked on the AWOS III-PT. Unless they have done something custom it doesn't use separate sensors for temperature and humidity. It uses a combination 5190-F temperature/humidity sensor inside the 8190 MARS.

Interesting!

My local airport, KSAW, seems to run about 2-3 degrees low lately in dewpoint as compared to other airports/RAWS stations. Just checked the spec and max error is 3F between +30 and +90F. So, I guess they're within spec!

Do the AWOS IIIP/T capacitive sensors tend to drift noticeably and, if so, which direction is typical?

Also, any idea of the aspiration rate (m/s, cfm, whatever)?

The 5190 can drift as much as 1% per year and tends to lean on the wet bias side when it does drift. The 8190 MARS aspirates at 360ft/min. The typical problem I see with AWOS systems is the lack of a consistent maintenance schedule.
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Offline kcidwx

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #58 on: July 28, 2018, 03:03:46 PM »
Nice info in this thread. Thanks guys.


KCID...do you have any spec documentation for the DTS1? I can't find much through Google.

Relative humidity measurement: Measurement range: 0-100%RH; Accuracy at 68F: +-1.0% RH (0-90%RH), +-1.7%RH (90-100%RH); Sensor: Vaisala HUMICAP 180 Vaisala HUMICAP 180R

Accuracy (Including Non-linearity, Hysteresis, and Repeatability)
At +15 ... +25 C (+59 ... +77 F)1 %RH (0 ... 90 %RH)
1.7 %RH (90 ... 100 %RH)
At −20 ... +40 C (−4 ... +104 F) (1.0 + 0.008 reading) %RH
At −40 ... −20 C (−40 ... −4 F) (1.2 + 0.012 reading) %RH
At +40 ... +60 C (+104 ... +140 F)(1.2 + 0.012 reading) %RH
At −60 ... −40 C (−76 ... −40 F)(1.4 + 0.032 reading) %RH


The sensor outputs in DP.

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Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #59 on: July 28, 2018, 03:22:21 PM »
I haven't played with black yet but i used  Rust. flat white paint made for plastic and uv resistant. I am not sure how you tell if black will be absorbent or not, just thought black would absorb being black and all lol. Need a paint guru to chime in here. :???:
Not a paint guru, so I'll just state what's probably more or less obvious.  If you paint the inside of your shield you better give the paint plenty of time to dry before putting the sensor in, as there seems to already be a lot of concern about contamination.  Also I would be a little concerned about the paint, especially if low quality, eventually flaking and turning to dust, even though not in direct sunlight, possibly causing more problems.
Absolutely...'out-gassing' of paint volatile's will detrimentally affect RH sensor accuracy.

I thought about that so painted them last week when they first arrived so they had at least 5 days of drying time.  Also open air outside I hope alls well. Did hit 98% on humidity today both stations.

Randy

Offline CW2274

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #60 on: July 28, 2018, 03:29:09 PM »
Yes, they do. I've worked on the AWOS III-PT. Unless they have done something custom it doesn't use separate sensors for temperature and humidity. It uses a combination 5190-F temperature/humidity sensor inside the 8190 MARS.

Interesting!

My local airport, KSAW, seems to run about 2-3 degrees low lately in dewpoint as compared to other airports/RAWS stations. Just checked the spec and max error is 3F between +30 and +90F. So, I guess they're within spec!

Do the AWOS IIIP/T capacitive sensors tend to drift noticeably and, if so, which direction is typical?

Also, any idea of the aspiration rate (m/s, cfm, whatever)?
The typical problem I see with AWOS systems is the lack of a consistent maintenance schedule.
I'm sure there are exceptions, but ASOS's are placed at larger airports that handle more passenger traffic than say, at a strictly GA airport and are serviced by NWS or FAA techs. AWOS's are usually at the, as we say, "dink" airports and are "serviced" by airport management.
Like I said, I'm sure one size doesn't fit all.

Offline Old Tele man

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #61 on: July 28, 2018, 03:49:07 PM »
Yes, they do. I've worked on the AWOS III-PT. Unless they have done something custom it doesn't use separate sensors for temperature and humidity. It uses a combination 5190-F temperature/humidity sensor inside the 8190 MARS.

Interesting!

My local airport, KSAW, seems to run about 2-3 degrees low lately in dewpoint as compared to other airports/RAWS stations. Just checked the spec and max error is 3F between +30 and +90F. So, I guess they're within spec!

Do the AWOS IIIP/T capacitive sensors tend to drift noticeably and, if so, which direction is typical?

Also, any idea of the aspiration rate (m/s, cfm, whatever)?
The typical problem I see with AWOS systems is the lack of a consistent maintenance schedule.
I'm sure there are exceptions, but ASOS's are placed at larger airports that handle more passenger traffic than say, at a strictly GA airport and are serviced by NWS or FAA techs. AWOS's are usually at the, as we say, "dink" airports and are "serviced" by airport management.
Like I said, I'm sure one size doesn't fit all.

Yep, I've noticed local airports KVAQ and KRYN exhibit lots of 'questionable' data variability compared to local international airport KTUS and USAF base KDMA...there seldom are agreements in their temp, DP or ALT readings.
« Last Edit: July 28, 2018, 03:51:38 PM by Old Tele man »
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Offline jgentry

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #62 on: July 28, 2018, 04:03:29 PM »
I think the only way to properly test is having matching thermometers. These SHT31's are all the same within .1F  but
if anyone wants to follow this Davis station with 7714 pictured above and airport ASOS I'll add links with 5 minute updates.


links with 5 minute updates about 2 miles distance.

https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=E7498
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVTN&unit=0&timetype=LOCAL/

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See where your 31 went up to 100% today.

So far, the DP is matching up with the Airport
Davis Vantage Pro2. SHT 31. 24hr FARS. WU: KXALJEMI2 & KALTHORS2 CWOP: C6353 & C6358

  

Offline graculus

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #63 on: July 28, 2018, 04:22:52 PM »
VP2 ISS Upgrade Kit:

7714 shield with SHT-??
Rainwise gauge
Real NEMA enclosure for the ISS electronics board

 ;)

Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #64 on: July 28, 2018, 05:09:52 PM »
I think the only way to properly test is having matching thermometers. These SHT31's are all the same within .1F  but
if anyone wants to follow this Davis station with 7714 pictured above and airport ASOS I'll add links with 5 minute updates.


links with 5 minute updates about 2 miles distance.

https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=E7498
https://mesowest.utah.edu/cgi-bin/droman/meso_base_dyn.cgi?stn=KVTN&unit=0&timetype=LOCAL/

 [ You are not allowed to view attachments ]

See where your 31 went up to 100% today.

So far, the DP is matching up with the Airport

 I use Cumulus and can select use 100% for 98%.  They did reach 98% just not 100%. This was in light fog nothing real soupy. I was thinking about the ASOS how sensor is exposed and wonder if that's not also an issue with ours being inside a shield with a filter. 98% may be max in certain environments....Just a :idea:
Randy

Offline SnowHiker

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #65 on: July 29, 2018, 12:15:00 AM »
Flat Black and Gloss White...but I'm interested to hear what others use.
I was wondering about some kind of tape for the black that could be used to line the chamber?  Seems like it would be safer than paint, and easier to remove if needed, depending on the adhesive used.  My first thought was electrical tape, but it would probably be too shiny.  Maybe some kind of gaffer's tape or something?


Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #66 on: July 29, 2018, 05:23:50 AM »
Tape has adhesive on the back which may last much longer. The paint issue is legit concern also, at the time main concern was making the passive shield as good as possible and wasn't planning on putting new sensors in but that has changed now where the passive will be primary shield especially at remote site which is totally wide open with wind movement I have little concern but in town backyard less wind, I still need to test before satisfied.   

Hoping for some calm mostly cloudless hot days ahead for good testing.
Primary concern is sunny calm days I'm not getting max temperature spikes the passive shields are famous for, and so far only .6 which is very acceptable even fars shields 1 difference is common on high temperatures, usually less differential on lows. 
 
Randy

Offline Bobvelle

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #67 on: July 29, 2018, 01:54:44 PM »

Absolutely, 'out-gassing' of paint volatile's will detrimentally affect RH sensor accuracy.
As in Permanently ruin it ?  :shock:

Offline DaleReid

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #68 on: July 29, 2018, 02:00:51 PM »
Titanium dioxide based white paint, its what they use on the National Solar Observatory Telescope which was on Kitt Peak.

If it is good enough for the research guys, it should be good enough for us.

PS, no idea where they get the stuff.  Maybe an auto paint store which seems to be able to get just about anything might do?
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Offline Bobvelle

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #69 on: July 29, 2018, 02:01:53 PM »
I'm starting this test over today because the first day shield being used was modified with bottom removed so I could insert another sensor inside.

I know we are talking about 2 different shields here but on the 7710, is the recommended mounting location back on the "biscuit disk" hanging from the plate above? I know of three different mount options.. one even uses 1 inch stand-offs. How are you mounting the sensor board?

Offline SLOweather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #70 on: July 29, 2018, 02:02:11 PM »
Probably not. As I recall, you can bake the sensor to recondition it. See the Sensirion handling docs and spec sheets.


Absolutely, 'out-gassing' of paint volatile's will detrimentally affect RH sensor accuracy.
As in Permanently ruin it ?  :shock:

Offline jgentry

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #71 on: July 29, 2018, 02:02:41 PM »
I'm starting this test over today because the first day shield being used was modified with bottom removed so I could insert another sensor inside.

I believe this was allowing reflective heat waves inside sensor chamber causing a slight warming. I went back to stock shield with AC fan today. I'm currently seeing FARS running .3 to .5 F cooler with completely stock shield. Still not bad for passive but will need to continue testing.
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How is your test turning out?
Davis Vantage Pro2. SHT 31. 24hr FARS. WU: KXALJEMI2 & KALTHORS2 CWOP: C6353 & C6358

  

Offline Bobvelle

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #72 on: July 29, 2018, 02:06:29 PM »
Titanium dioxide based white paint, its what they use on the National Solar Observatory Telescope which was on Kitt Peak.

If it is good enough for the research guys, it should be good enough for us.

PS, no idea where they get the stuff.  Maybe an auto paint store which seems to be able to get just about anything might do?

TiO2 standard white pigment... Titanium white is the color.

Online ValentineWeather

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #73 on: July 29, 2018, 02:21:51 PM »
Question asked on mounting it has good options even for multiple sensors if wanted using existing holes with screws.
Testing still in infancy nothing but rain and clouds.

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Randy

Offline Bobvelle

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Re: WMO field study thermometer shield FARS 7755, Passive 7714
« Reply #74 on: July 29, 2018, 02:41:13 PM »
Probably not. As I recall, you can bake the sensor to recondition it. See the Sensirion handling docs and spec sheets.


Absolutely, 'out-gassing' of paint volatile's will detrimentally affect RH sensor accuracy.
As in Permanently ruin it ?  :shock:
Thanks, Found it:  (This is for the SHT-15)
1.4 Reconditioning Procedure
As stated above extreme conditions or exposure to solvent
vapors may offset the sensor. The following reconditioning
procedure may bring the sensor back to calibration state:
Baking: 100 105C at < 5%RH for 10h
Re-Hydration: 20 30C at ~ 75%RH for 12h


I wonder how low Rh my oven gets? Likely not <5%. Not in a Gulf Coast region household oven anyway.
.

 

anything