Author Topic: High Temp inside Radiation Shield  (Read 762 times)

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Offline derek73

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High Temp inside Radiation Shield
« on: April 05, 2017, 02:28:57 AM »
Hi, I bought a Davis 7714 radiation shield but I notice that the temperatures at night is too high.  If I have the sensor outside the shield, it is very accurate when looking at other local readings but inside the shield it is around 2-3C higher.

Is the shield that is meant to protect the sensor from sun and radiation also not allowing the cool air in, resulting in innacurate night time temps?

Offline johnd

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Re: High Temp inside Radiation Shield
« Reply #1 on: April 05, 2017, 03:04:52 AM »
Sky conditions overnight are relevant too. Do you notice better agreement on cloudy nights compared to clear nights?

But in general I'd believe the temperature inside the shield. Any sensor outside a shield and able to see the sky directly is going to read too low on clear nights because of radiation effects.
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Offline ValentineWeather

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Re: High Temp inside Radiation Shield
« Reply #2 on: April 05, 2017, 06:05:23 AM »


Is the shield that is meant to protect the sensor from sun and radiation also not allowing the cool air in, resulting in innacurate night time temps?

Haven't actually tested this unit but answer is most likely No. Remember radiation shields not only protect from sun but radiational cooling at night. This is the surface cooling you seen on objects with clear skies, IE frost on windshield when temperature is above freezing.  You very likely live in a warmer area like ridge top, hill vs in a valley area where colder air collects is why you see the nighttime difference.
Randy

Offline derek73

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Re: High Temp inside Radiation Shield
« Reply #3 on: April 05, 2017, 07:27:41 AM »
Thanks for both replies. This is a new unit so not too many nights that have been cloudy so far, some clear nights and some nights of clear spells / partly cloudy. I guess that I am assuming that professional readings from the Internet are correct but of course they are not taking readings from my garden :)

I need to learn to trust the readings that I have and trust the shield.


Offline DoctorKnow

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Re: High Temp inside Radiation Shield
« Reply #4 on: April 05, 2017, 08:10:06 AM »
Where is your thermometer located? Out in the open away from trees and buildings, or mounted on your house or shed, a tree etc?


Offline derek73

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Re: High Temp inside Radiation Shield
« Reply #5 on: April 05, 2017, 08:20:56 AM »
On a wooden post in the middle of my lawn. Mounted 4ft high.

Offline DoctorKnow

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Re: High Temp inside Radiation Shield
« Reply #6 on: April 05, 2017, 08:40:40 AM »
As long as you aren't under a tree, I would trust the reading. Usually when people find their readings a bit high, it's because of the siting. I've experimented many times, by having thermometers in trees, and under eaves. Each time, my temps are several degrees off. Temperature can and does vary some from what people a few blocks away are reporting too.