Author Topic: Mitigating Pressure Reading Errors  (Read 817 times)

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Offline TheBushPilot

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Mitigating Pressure Reading Errors
« on: November 09, 2022, 12:15:56 PM »
I notice a lot of these commercially available weather stations lack the ability to mitigate pressure errors induced by wind. Since most commonly (from what I understand) the little transducer is located within the console. Shouldn't there be more care taken into consideration for the affects of dynamic pressure from buildings? (Since most often the consoles are found within them.) Is it a convenience thing? Do people simply not care? Do the transducers require a significant amount of power requiring them to be put within something that has wall power versus say a Davis ISS with a super capacitor? Or maybe it's a price/performance thing?

Continuing with the Davis example, since they already supply a variety of parts and addons for their stations, would it be hard to introduce the ability to further improve pressure accuracy? I of course don't work for the company and don't know how difficult it would be to alter something of that magnitude within the station. Seems like a long neglected part of remote sensing - or perhaps misunderstood. Would be interesting to see though.

Just food for thought, let me know what you think.

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Offline gszlag

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Re: Mitigating Pressure Reading Errors
« Reply #1 on: November 10, 2022, 08:50:22 AM »
I notice a lot of these commercially available weather stations lack the ability to mitigate pressure errors induced by wind. Since most commonly (from what I understand) the little transducer is located within the console. Shouldn't there be more care taken into consideration for the affects of dynamic pressure from buildings? (Since most often the consoles are found within them.) Is it a convenience thing? Do people simply not care? Do the transducers require a significant amount of power requiring them to be put within something that has wall power versus say a Davis ISS with a super capacitor? Or maybe it's a price/performance thing?

Continuing with the Davis example, since they already supply a variety of parts and addons for their stations, would it be hard to introduce the ability to further improve pressure accuracy? I of course don't work for the company and don't know how difficult it would be to alter something of that magnitude within the station. Seems like a long neglected part of remote sensing - or perhaps misunderstood. Would be interesting to see though.

Just food for thought, let me know what you think.

Cheers

Lots of very interesting questions.

The earth's atmosphere has weight to it and that is what a barometric sensor measures. When the atmosphere moves around a lot (think hurricane winds), you can certainly feel it. I have observed that a sensitive barometer can measure these fluctuations due to wind – as it should.
If pressure fluctuates from wind, a hurricane or a volcanic explosion – I want to see it. If I am calibrating though - I don't want to see it!

A you know, when airplanes are flying the rush of wind would definitely make pressure readings difficult so the flying barometer (altimeter) mitigates the effects of wind using a static port. Land based barometers located inside an equipment rack inside an aerodrome also uses a static port to the outside of the building to mitigate the effects of air conditioning, fresh air exchangers, doors opening and closing, etc.

I am not a big fan of having sensors enclosed in a console – although for different reasons. If a temperature, humidity or barometric sensor fails, how are you going to fix it? If the sensors become deprecated as technology improves how are you going to upgrade it? The answer is – with great difficulty.

Getting back to you barometric pressure question....yes, homes are susceptible to the same issues as an aerodrome but to a far lesser degree. Some consumer grade sensors can automatically dampen the pressure fluctuation of a door slam. Also, our consumer grade sensors aren’t going to measure a 0.05 hPa blip. They are just too slow, noisy to resolve to that level.

Inside vs outside barometric sensors? Here in Canada, airport baros are usually inside although for remote weather stations and buoys all sensors are obviously outside. For consumer grade personal weather stations it could be a price/performance issue as an outside barometric sensor would have to include a precision temperature compensating circuit. I am not an electronics engineer but my understanding is that this compensating circuit keeps readings accurate as outside temperature changes. Depending on the design, some sensors can’t tolerate much dust or moisture  so mitigating these effects would drive up costs for an outside barometric sensor.

The best way to improve the accuracy of our barometers is to upgrade them every few years as sensor accuracy/precision  is growing by leaps and bounds. That’s an expensive proposition if the sensor(s) are soldered onto a PCB inside a console. So you are correct – remote sensing is the clear answer but an inside barometric sensor (like the airport) is more than good enough. Or you can spring for a commercial-grade Vaisala with a static port.  I think Dale might have experience with Vaisala weather stations and/or sensors..
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Offline TheBushPilot

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Re: Mitigating Pressure Reading Errors
« Reply #2 on: November 10, 2022, 02:43:50 PM »
I am not a big fan of having sensors enclosed in a console – although for different reasons. If a temperature, humidity or barometric sensor fails, how are you going to fix it? If the sensors become deprecated as technology improves how are you going to upgrade it? The answer is – with great difficulty.

Fair point, I hadn't even thought about reparability. Would it be so hard to manufacture them with removable sensor components? I'm not really familiar with those types of sensors but surely they are designed to be popped in and out if the receiving board was configured as such no? Maybe that's by design. Force the customer to return back to the manufacturer if something goes awry or like you said make it extremely difficult to do it oneself.

Getting back to you barometric pressure question....yes, homes are susceptible to the same issues as an aerodrome but to a far lesser degree. Some consumer grade sensors can automatically dampen the pressure fluctuation of a door slam. Also, our consumer grade sensors aren’t going to measure a 0.05 hPa blip. They are just too slow, noisy to resolve to that level.

Well that's interesting. I didn't know they could dampen. I guess the advantage of cheaper transducers is they don't detect everything, only what matters I suppose. Especially considering pressure measurements are more of a macroscale measurement. And in the case of placement inside buildings despite having some influence, the slow response time makes them less susceptible to those dynamic influences.

Inside vs outside barometric sensors? Here in Canada, airport baros are usually inside although for remote weather stations and buoys all sensors are obviously outside. For consumer grade personal weather stations it could be a price/performance issue as an outside barometric sensor would have to include a precision temperature compensating circuit. I am not an electronics engineer but my understanding is that this compensating circuit keeps readings accurate as outside temperature changes. Depending on the design, some sensors can’t tolerate much dust or moisture  so mitigating these effects would drive up costs for an outside barometric sensor.

The best way to improve the accuracy of our barometers is to upgrade them every few years as sensor accuracy/precision  is growing by leaps and bounds. That’s an expensive proposition if the sensor(s) are soldered onto a PCB inside a console. So you are correct – remote sensing is the clear answer but an inside barometric sensor (like the airport) is more than good enough. Or you can spring for a commercial-grade Vaisala with a static port.  I think Dale might have experience with Vaisala weather stations and/or sensors..

That's a really good point. I didn't even think about the temperature dependencies. Something I'll admit I've taken for granted with the commercial instruments. Makes absolute sense for the manufacturer to put the temperature sensitive components in the climate controlled environment versus out with the rest of the system. I don't know all there is to know about the circuits either but I'd assume it would substantially increase the cost if they implemented it. A give take scenario if you will. Cheap sensor that's accurate enough but will only perform well in a specific temperature range, and despite external factors possibly inducing error it isn't enough to justify a complete overhaul of the system. Maybe I haven't given these brands enough credit...? :-s

I'd consider adding a barb to the pressure sensor to accept hosing for an external pressure port, but the temperature dependency consideration, and dirt/debris, you'd probably have to redesign the whole apparatus. A rabbit hole for something one could achieve by simply investing in a more robust instrument. :roll:

Thinking about it a little more, it makes total sense airports would keep the pressure transducers indoors. I know a common manufacturer they use is Setra. The 470's employed have an accuracy of 0.02% @ 21°C. Keeping them in a controlled environment eliminates a significant source of error and probably prolongs their lifespan as well. Easily done with their placement indoors directly integrated within the central processing rack. Win win.

Very very interesting points and lot's to think about.

Cheers
"There is — always — more than one thing influencing anything we are trying to measure." ~ Sherman Fredrickson
"Do it right or don't do it at all."

Met Instruments Project
Central Chasers

 

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