Author Topic: Nimbus MMTS, Davis 7714, Davis DIY FARS compare  (Read 938 times)

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Offline ValentineWeather

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Nimbus MMTS, Davis 7714, Davis DIY FARS compare
« on: April 14, 2024, 11:53:14 AM »
Added a website camera for a (3) shield comparison between the MMTS, Davis 7714 along with the DIY FARS which is the primary thermometer in real-time. If you want to compare, the camera link updates every 1-minute.  Yesterday the Miller Field ASOS set a record high 91, both the FARS and Davis 7714 matched while the MMTS with the Nimbus was cooler at 89. 
May only do this for a while, normally just have the Nimbus on the camera. I thought some of the other weather enthusiast may be interested. The MMTS appears to be running cool during the daytime, it was running about the same during our winter temps, but now running cooler. Haven't had a day when it's calm, today may be one of the less windy days, sub 20 mph anyway. 

The camera link is: https://www.valentinenebraska.net/camera.php    The FARS is far right, 7714 middle.
« Last Edit: April 19, 2024, 09:55:29 PM by ValentineWeather »
Randy

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #1 on: April 14, 2024, 09:40:41 PM »
Interesting that the MMTS is running cooler. Sounds like with a lower max its not even really attributed to lag. I noticed today that the 7714 and the FARS seemed to match pretty closely with the MMTS cooler (2F at times when I looked today). As the sun goes down, I wonder if everyone will come back together. Any thoughts as to what youre seeing? Will be interesting to see a hot calm wind day.

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #2 on: April 14, 2024, 10:27:21 PM »
Yes the MMTS ran 2 cooler all day. The 7714 and FARS are running close with the breeze we have, it would be different if it got calm but today there was 10-15 mph breeze. Today highs fars-80.0, 7714-80.1, mmts-78.3, airport asos-80 at 1.8 miles away.
Jerry has been watching it too, and we are both stumped. In the winter they were running close most of the time and never anything like 2 cooler like now with the warmer temps. Now the low temps are still close together, the FARS was coolest this morning 46.0, MMTS 46.2 and 7714 was 46.5.   Head scratcher  #-o right now trying to figure out why the big difference with the warmer temps. Is it a calibration issue? These Nimbus units I read are calibrated at the factory. I know the wire run here is much longer than what it was at the old location.
Randy

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #3 on: April 18, 2024, 04:08:55 PM »
I wonder if it continues the practicality of collocating a Davis sensor or other sensor of known accuracy in the MMTS shield? Any insight on who manufactures that shield? Ive searched in vain.

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #4 on: April 18, 2024, 05:58:10 PM »
I wonder if it continues the practicality of collocating a Davis sensor or other sensor of known accuracy in the MMTS shield? Any insight on who manufactures that shield? Ive searched in vain.

Same here, I couldn't find anything on the shield maker, wonder if it wasn't just a one time outside contract due to the fact parts are scarce. I was told this on installation they have to reuse connectors because they are no longer made.

Provided the Nimbus sensor is correct. It's running cooler than the SHT-31 FARS by as much as 2 once we reached into the low 90s one day.  Guess the best way to know for sure would be to open the shield and insert a SHT-31 inside and see how it compares with the nimbus probe.  I did read somewhere when they started replacing the CRS with the MMTS they noticed about a degree cooler on the MMTS. 
I can say the airport ASOS is right with the FARS SHT-31 most days for highs. While the MMTS will lag back a bit on some days. 
Randy

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #5 on: April 18, 2024, 08:05:31 PM »
Yes, thats exactly what I was thinking. Trying to see if the difference is a function of the shield or the sensors

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #6 on: April 18, 2024, 11:17:51 PM »
Also, does your Nimbus say who manufactures those displays these days?

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #7 on: April 19, 2024, 07:15:08 AM »
Randy

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #8 on: April 19, 2024, 07:48:38 AM »
Thanks. I thought someone else might be making them now. From what I can tell, Sensor Instruments Co has been defunct for quite some time.

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #9 on: April 19, 2024, 09:32:50 AM »
I've got a spare 25' SHT-31, and may try to feed it up though the mounting pipe. It may go on its own, but may not. If not, have to find something flexible to guide it.
Really don't want to open the shield up if I don't have to. You can see the Nimbus sensor is located at the bottom of the shield and offset to the side. Need to plug that PVC hole anyway to prevent bugs from entering.

Randy

Offline CW7491

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #10 on: April 19, 2024, 11:52:22 AM »
I think it would be informative if the discrepancy continues in warmer weather. I suspect its the coop sensor, not the shield.

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #11 on: April 19, 2024, 02:06:32 PM »
Can't be done  :-(  , I looked inside solid plates, really no way to get another probe inside without some kind of shield modification by drilling a hole and won't being doing that since it's not mine. We'll just have to assume it's the sensor and not the shield making the difference. See what happens once we get into the warmer temps and light wind.
Randy

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #12 on: April 19, 2024, 02:24:10 PM »
Thanks for trying

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #13 on: April 19, 2024, 04:23:20 PM »
It's not the shield has to be the sensor, we have a stiff breeze in the mid 40's and a full degree difference.
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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #14 on: April 19, 2024, 08:22:57 PM »
Yeah, that's just not right. To be honest, it's not that surprising considering the NWS is using equipment manufactured by a company that went defunct nearly 15 years ago. It comes down to cost I assume. Lots more user friendly technology available now with the ability for better siting. The issues with the current MMTS system have been documented. Although the radiation shield seems to work well. Even Davis published a study in comparison around 2007 and ran into problems https://ams.confex.com/ams/87ANNUAL/techprogram/paper_118190.htm

I was also surprised they accepted this COOP MMTS tying of the Utah state temperature record on siting alone ...
https://www.ncei.noaa.gov/monitoring-content/extremes/scec/reports/20220708-Utah-Maximum-Temperature.pdf

ASOS isn't immune either though as I posted elsewhere a really interesting video from NWS Louisville KY documenting the extremely lax tolerances at the Lexington KY ASOS. At least a fix there is in the works ...
« Last Edit: April 20, 2024, 08:46:07 PM by CW7491 »

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compair
« Reply #15 on: April 19, 2024, 09:47:26 PM »
WOW, I can't believe they accepted the UTAH record High from that location. Notice the FARS read about a degree lower, so they thought it was all good. WHAT? That location doesn't meet siting guidelines for temperature or rainfall.
And that's a block fence, they get hotter than hell. And so close to the house.
I don't get it at all.
« Last Edit: April 19, 2024, 09:50:35 PM by ValentineWeather »
Randy

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compare
« Reply #16 on: April 19, 2024, 10:42:59 PM »
It is crazy. Did you notice the picture of the RAWS site they disqualified? I cant speak to the instrumentation, but the siting looks exceptional. Ive been waiting, for years now, on the 130F Death Valley temp. The climate extremes committee are looking at one from 2020 and 2021. Still nothing out. Speculation that they might be considering decertifying the 134F record.
https://stormbruiser.com/chase/2023/11/29/the-death-valley-temperature-record-is-being-fought-over/

In any case, the Furnace Creek station used the CS215 temp/rh probe which utilizes the SHT75. Its crazy to me they were using that sensor (in a tiny, poorly sited passive shield) at a climate station with that kind of public interest.

At least Dr Baker and Campbell Scientific seem to have a serious interest
https://www.campbellsci.com/blog/death-valley-collaboration-update
https://stormbruiser.com/chase/2022/09/06/detailed-afternoon-temperature-comparisons-at-furnace-creek-in-death-valley-in-july-2021/

But I digress

Offline ValentineWeather

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compare
« Reply #17 on: April 19, 2024, 11:14:12 PM »
I saw a poll today: Do you trust our government? About 90% said NO.
I'm still flabbergasted by that Utah siting. Even all the concrete around there should have disqualified the record temp, so it actually fails in every siting guideline there is for temperature. I would say the temp was at least +4 maybe even +6 of actual.
Randy

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Re: Nimbus MMTS, Davis 7714, Davis DIY FARS compare
« Reply #18 on: April 19, 2024, 11:19:18 PM »
I saw a poll today: Do you trust our government? About 90% said NO.
Surprised it's that low....

 

anything