Author Topic: Barani pro passive shield  (Read 6411 times)

0 Members and 1 Guest are viewing this topic.

Offline jerryg

  • Forecaster
  • *****
  • Posts: 738
  • weather is never boring
    • victoria texas weather
Barani pro passive shield
« on: August 18, 2018, 09:35:15 AM »
I wanted to start a new thread about the pro and standard Barani Designs passive shield and how it works in the backyard of normal pws, any professional studies and comparisons can be found on the Barani home page. And to start i finally got a morning with no wind and no clouds on the horizon to block the sun so i could see how the shields i have in use compared when the sun was hitting the plates at maximum exposure. The standard shield gets some morning shade from my tower and it and the fars which is in full sun ran the same temp. The pro ran about .4 to .5 higher until the wind picked up and then it was running the same as the others. I just want to add that i came up with the top plate idea about adding shade to the shield and passed it along to Valentine, so my bad if it upset the purist in the group. I am always trying different things to improve my readings and will keep doing so. I got the idea of the top plate from looking at the high dollar shields they use on the climate research stations which spec at less than .05F added to temp. The shield is a 3 tube design but has a single large plate that shades the tubes in the heat of the day and i thought if it's good enough for them i would try it and it works. So don't blame Valentine for the idea we both like to try out various things, some work some don't. We both have some sensor housing coming that we will be trying out. So any of you who are thinking about trying a better passive shield then hang it there for further reports. Hey remember the cotton region shelter was the best at the time then someone decided to add the second set of louvers and that became the best then someone said why white inside lets paint it black and absorb radiation inside the shield and that became the best and along came the gill plate design and again the best until the fan was added now that is the standard, so finding better ways of housing sensors is always ongoing  =D>

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #1 on: August 18, 2018, 10:26:02 AM »
Awesome Jerry.
If I get any new info I'll drop in. 
Was up until 1am last night setting up my test shields. Think my neighbors wonder what I'm smoking.  :lol:
Randy

Offline jerryg

  • Forecaster
  • *****
  • Posts: 738
  • weather is never boring
    • victoria texas weather
Re: Barani pro passive shield
« Reply #2 on: August 18, 2018, 10:44:53 AM »
Ha, i have that over you, where i live out in the country i have no one to know i am crazy with all the stuff i have out on the weather tower  :lol: . Just a funny note i had a guy going down the road who stopped an asked what i was doing with all the bee hives, i was trying out several cotton regional shelters  :lol:.

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #3 on: August 18, 2018, 01:42:30 PM »
With a little wind seeing the pro do better today, Only by 1/2 degree. 
 [ You are not allowed to view attachments ]
Randy

Offline jerryg

  • Forecaster
  • *****
  • Posts: 738
  • weather is never boring
    • victoria texas weather
Re: Barani pro passive shield
« Reply #4 on: August 18, 2018, 02:22:14 PM »
Need to do a little updating, finally some weather that lets me check things out with low wind speed and sunny. It looks like the oversize plate on top of the pro and standard shield are doing a pretty good job. The pro has been running around a degree lower than the fars and the standard shield has been around half degree lower. When a cloud comes over the fars temp drops pretty quickly down to the pro temp and so does the standard. The pro only drops a few tenths with cloud cover and when the cloud moves by the pro goes up a few tenths and the fars goes back up to the 1 degree higher which shows the fars temp is being affected by the solar heating of the sun on the shield which is shown in the specs of the shield. I think later in the year when the solar energy is a lot lower the plate won't be necessary and the sun angle will probably be too low for an overhead plate to do any good. With the plate atop the two shields when the wind was calm or low the temp of the pro got withing half a degree of the fars on the low side and the standard went up to the fars temp. 

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #5 on: August 18, 2018, 02:57:32 PM »
Jerry I possibly see why on your end you see the Davis FARS running so much higher than I do. My FARS is only .4 or so higher vs the Pro with a breeze continuously. You see over a full degree F.
You are using the stock fan correct?  I use a more powerful AC fan. Back Pressure from the wind is hampering the stock fan.

This is exactly what the WMO study said!  The Davis FARS ran warmer with wind... Bingo  \:D/
Randy

Online openvista

  • Forecaster
  • *****
  • Posts: 388
    • marquetteweather.com
Re: Barani pro passive shield
« Reply #6 on: August 18, 2018, 03:09:57 PM »
...the fars goes back up to the 1 degree higher which shows the fars temp is being affected by the solar heating of the sun on the shield which is shown in the specs of the shield...

I would argue that all Davis specs are suspect after the move they've pulled with humidity. In any event, Davis is assuming you're using their fan and power section that produces just under 1 m/s flow in the daytime. If memory serves you're running the fan at 3V off a wall wart during the day, but I'm not sure how much that increases the fan rate. Any idea?

According to the research I've read, 1 m/s is the line below which significant errors occur. The pro/reference gear is all above 2 m/s (much of it 3 m/s or higher) to avoid under aspiration.
Davis Vantage Pro2 FARS | https://marquetteweather.com | EW7933

Online openvista

  • Forecaster
  • *****
  • Posts: 388
    • marquetteweather.com
Re: Barani pro passive shield
« Reply #7 on: August 18, 2018, 03:15:06 PM »
This is exactly what the WMO study said!  The Davis FARS ran warmer with wind... Bingo  \:D/

Except that he said his winds were low.
Davis Vantage Pro2 FARS | https://marquetteweather.com | EW7933

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #8 on: August 18, 2018, 03:39:24 PM »
This is exactly what the WMO study said!  The Davis FARS ran warmer with wind... Bingo  \:D/

Except that he said his winds were low.

Low to Jerry may be what I'm seeing today from basically 0 mph first few days to around 6-8 mph at surface feels like a hurricane.  :lol:
Just with that amount of wind my Pro shield is running lower around .3F over AC fars,  I'll post a graph later this evening. We do have storms coming so maybe earlier actually. 
Randy

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #9 on: August 18, 2018, 03:53:30 PM »
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.


 [ You are not allowed to view attachments ]
 [ You are not allowed to view attachments ]
« Last Edit: August 21, 2018, 06:56:20 AM by ValentineWeather »
Randy

Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #10 on: August 18, 2018, 04:11:28 PM »
I sent these graphs to Barani explaining this is even with higher powered fan not stock.
Randy

Offline jerryg

  • Forecaster
  • *****
  • Posts: 738
  • weather is never boring
    • victoria texas weather
Re: Barani pro passive shield
« Reply #11 on: August 18, 2018, 04:36:02 PM »
I am running 2.3 volts on the fan, near the same as the solar panel, i have it set to cut off at night to avoid messing up my sensor with too much moisture input. My shield is a 14 inch round tray with a 1 inch lip that was dark gray so no paint on bottom and painted white on top. I have been watching the temp of the fars vary as much as 1 degree between sunshine and when a cloud comes over. If you forget the temp. part of this i look at it this way the fars has a fan that dies or sticks, batteries to run at night if using solar, gets real dirty shield and filter, needs cleaning and if using solar batteries may not run all night if not getting good charge during day time because of clouds or amount of sun time available in the winter and higher latitudes. Now the Barani unique design keeps shield and sensor filter cleaner, less cleaning time, no problem with sensor getting overly wet, response seems better, the stuff the shield is made from is slick so water doesn't remain on the plates and dirt and bugs slide off, it says lol. A lot of this has to be seen in the long term and hope it all comes to pass.
« Last Edit: August 18, 2018, 04:38:10 PM by jerryg »

Offline hwcorder

  • Contract Weather Observer at KCLT
  • Senior Member
  • **
  • Posts: 73
Re: Barani pro passive shield
« Reply #12 on: August 18, 2018, 04:48:15 PM »
Need to do a little updating, finally some weather that lets me check things out with low wind speed and sunny. It looks like the oversize plate on top of the pro and standard shield are doing a pretty good job. The pro has been running around a degree lower than the fars and the standard shield has been around half degree lower. When a cloud comes over the fars temp drops pretty quickly down to the pro temp and so does the standard. The pro only drops a few tenths with cloud cover and when the cloud moves by the pro goes up a few tenths and the fars goes back up to the 1 degree higher which shows the fars temp is being affected by the solar heating of the sun on the shield which is shown in the specs of the shield. I think later in the year when the solar energy is a lot lower the plate won't be necessary and the sun angle will probably be too low for an overhead plate to do any good. With the plate atop the two shields when the wind was calm or low the temp of the pro got withing half a degree of the fars on the low side and the standard went up to the fars temp.

I earlier (in other post) asked about that circular (pizza) plate above the Barani Pro passive shield because previously I did something similar for my LaCrosse WS-8610 wireless weather unit...only I used a circular piece of perforated sheet metal from Home Depot. Did this mod in an attempt to mitigate the "heat-of-the-day" temperature HUMP that occurred with the wimpy stock OEM LaCrosse solar "shield." Was able to reduce solar effects from 3-4F down to 1-2F using the perforated metal 'shield' above the LaCrosse unit same as you've done. I used the perforated sheet metal because it was less prone to "flying" in high-wind situations. It was flat, but I believe having it rounded or domed downward would probably work better.

What are your thoughts?

Some of the "professional" passive radiation shields have the bowl design up top for extra protection against higher solar angles. This one is from Comet.


Offline ValentineWeather

  • Forecaster
  • *****
  • Posts: 5362
Re: Barani pro passive shield
« Reply #13 on: August 18, 2018, 05:00:14 PM »
Nice I'll start looking for something like that.
The ASOS has a huge bowl on top also, I'm guessing in the 14" diameter range.
Randy

Online openvista

  • Forecaster
  • *****
  • Posts: 388
    • marquetteweather.com
Re: Barani pro passive shield
« Reply #14 on: August 18, 2018, 05:02:12 PM »
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.

For example, between 10-11AM winds are relatively low. Around 11AM wind speed rapidly doubles but the differential remains the same (and by my eye may even be a tad smaller). That's despite insolation continuing to rise which should create additional solar radiation errors assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

Maybe once winds get "high" the relationship is clear, but unfortunately the WMO didn't define what constitutes "high wind speed" for the Davis FARS.
Davis Vantage Pro2 FARS | https://marquetteweather.com | EW7933

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #15 on: August 18, 2018, 05:23:19 PM »
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?

Offline hwcorder

  • Contract Weather Observer at KCLT
  • Senior Member
  • **
  • Posts: 73
Re: Barani pro passive shield
« Reply #16 on: August 18, 2018, 05:55:35 PM »
Quote from: openvista LinkedIn=topic=34936.msg356736#msg356736 date=1534626132
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?
Pressure perturbations caused by airflow around the fars could disrupt the constant airflow through the sensor chamber. Makes sense as this would probably overcome a weaker fan like a stock one first.  Now turbo charge the fan like you have and it would take a stronger wind to cause any disruption.
« Last Edit: August 18, 2018, 05:58:09 PM by hwcorder »

Online openvista

  • Forecaster
  • *****
  • Posts: 388
    • marquetteweather.com
Re: Barani pro passive shield
« Reply #17 on: August 18, 2018, 05:58:47 PM »
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?

I was only attempting to show that even if you conceded the idea that "high winds" were the culprit for the discrepancy between the two shields, there appears to be no easily identifiable relationship between increased wind speed and shield temperature differential according to the graphs Randy just posted.
Davis Vantage Pro2 FARS | https://marquetteweather.com | EW7933

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #18 on: August 18, 2018, 06:00:41 PM »
Quote from: openvista LinkedIn=topic=34936.msg356736#msg356736 date=1534626132
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?
Pressure purterbations caused by airflow around the fars could disrupt the airflow through the sensor chamber.
Get that. The problem is that would be a momentary instance, an anomaly, not a continuous condition as is being reported.

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #19 on: August 18, 2018, 06:10:48 PM »
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?

I was only attempting to show that even if you conceded the idea that "high winds" were the culprit for the discrepancy between the two shields, there appears to be no easily identifiable relationship between increased wind speed and shield temperature differential according to the graphs Randy just posted.
I wasn't inferring that you were making crazy talk, if you thought I was, the contrary, I agree with you. Until there's empirical evidence to the contrary saying the breeze is responsible, I'll continue on my doubtful ways.

Offline jerryg

  • Forecaster
  • *****
  • Posts: 738
  • weather is never boring
    • victoria texas weather
Re: Barani pro passive shield
« Reply #20 on: August 18, 2018, 06:13:10 PM »
I have a question on this, i am in no way very knowledgeable about air flow, but i read in a thread that the fars was designed with an air intake that narrows down and causes an increase in air speed that is 2.4 times faster than if it was just an open tube. Wouldn't that help keep the wind from causing a disruption and warmer temps?

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #21 on: August 18, 2018, 06:20:57 PM »
Maybe this can be applied to the idea of a fan being overpowered by wind inside the sensor chamber.  But I'm no engineer just an ex operator.
Just an  :idea:
If, if the wind was at a constant velocity, I mean whereas an anomalous condition became the constant that defeated the purpose of the fan and/or chamber, I suppose I could get in line, but even this is pure conjecture. The wind is far to dynamic for this to occur IMHO.

Offline hwcorder

  • Contract Weather Observer at KCLT
  • Senior Member
  • **
  • Posts: 73
Re: Barani pro passive shield
« Reply #22 on: August 18, 2018, 06:22:33 PM »
Quote from: openvista LinkedIn=topic=34936.msg356736#msg356736 date=1534626132
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?
Pressure purterbations caused by airflow around the fars could disrupt the airflow through the sensor chamber.
Get that. The problem is that would be a momentary instance, an anomaly, not a continuous condition as is being reported.

We would have to know the wind speed where this occurs. Theoretically as long as the windspeed stays above that air could remain disrupted. Only way to really verify this would be to set this up in a wind tunnel with multiple pressure and airflow sensors.

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #23 on: August 18, 2018, 06:24:54 PM »
I have a question on this, i am in no way very knowledgeable about air flow, but i read in a thread that the fars was designed with an air intake that narrows down and causes an increase in air speed that is 2.4 times faster than if it was just an open tube. Wouldn't that help keep the wind from causing a disruption and warmer temps?
Can't answer that except that the 24hr FARS sensor chamber cylinder is the same diameter top to bottom.

Offline CW2274

  • Forecaster
  • *****
  • Posts: 3865
    • Conditions @ CW2274
Re: Barani pro passive shield
« Reply #24 on: August 18, 2018, 06:41:31 PM »
Quote from: openvista LinkedIn=topic=34936.msg356736#msg356736 date=1534626132
Check this out, with just a little wind even the AC FARS runs higher. Solar is much worse as Jerry has reported. I thought something was wrong but now I see what he's talking about. These Davis FARS are hampered by wind.

I see that once solar insolence reaches 500 W/m2 the temperature differential in the two shields is constant, regardless of wind speed.
 assuming the FARS sensor is inadequately ventilated compared to the Barani sensor.

This is crazy talk as far as I'm concerned. I'm not arguing that the FARS is reading slightly higher but blaming it on a breeze is nonsense in my eyes.
Someone please explain how a breeze going to stagnate air in the chamber, scientifically?
Pressure purterbations caused by airflow around the fars could disrupt the airflow through the sensor chamber.
Get that. The problem is that would be a momentary instance, an anomaly, not a continuous condition as is being reported.

We would have to know the wind speed where this occurs. Theoretically as long as the windspeed stays above that air could remain disrupted. Only way to really verify this would be to set this up in a wind tunnel with multiple pressure and airflow sensors.
Then this supposed problem would have been identified loooong ago, as keeping the air AOA the critical velocity (whatever that would be) occurs surely countless times every day. It's just a tad easier to have the wind above a certain point than it is to be at a constant, constantly.