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Author Topic: Surface Temp Sensor?  (Read 2240 times)

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Offline 2-Wheeler

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  • 48 13 07.05 N, 122 41 11.84 W, Elevation: 95 ft
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Surface Temp Sensor?
« on: October 04, 2006, 01:46:42 AM »
I am using the Davis VP2 with Soil Temp & Moisture sensors. I have one of the temp sensors in the soil about 6 inches below the surface and the readings are surprisingly stable. they tend to vary only a few degrees per day and tend to follow nearly the moving average for about the past 48 hours.

Now I've added a second soil temp sensor and want to use it for "surface temp".  So I have just laid the sensor on the ground and have been looking at the data. Of course it varies widely over the day. It also seems to rise and fall with cloud cover or lack thereof.  This is mostly what I expected. It seems to be picking up the solar heating of the surface.

Now I'm wondering if there is any way to improve the effect or representation of this surface temp. I've pondered the thought of attaching the sensor to the surface of an aluminium heat sink, which is placed on the ground. I've also thought of placing it on a black(or gray)-metal surface, which approximates the reflectivity of the soil.

Any other thoughts on this? Does anyone have any advice?

-David Broberg   CWOP#: CW5670 / CoCoRaHS #CO-BO-218

Offline dendrite

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  • Northfield, NH
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Re: Surface Temp Sensor?
« Reply #1 on: October 09, 2006, 03:45:03 PM »
Well...as it seems you know, an exposed sensor probe is going to give you probe surface temps, not ground surface temps. Sure, the readings will behave in much of the same way, but I'm not sure how representative the probe is to actual ground/grass. If you can find something with the same albedo as your particular surface type then I would think that would work. The albedo of specific materials is not my thing so I'm not much help. How would you describe your ground surface and soil type?

Offline niko

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Re: Surface Temp Sensor?
« Reply #2 on: October 09, 2006, 04:13:54 PM »
Even if you approximated the albedo of the surface, you would still have to approximate the heat sinking ability of the underlying earth to get a valid measurement.

Offline 2-Wheeler

  • Posts: 196
  • 48 13 07.05 N, 122 41 11.84 W, Elevation: 95 ft
    • CoupevilleWeather
Re: Surface Temp Sensor?
« Reply #3 on: October 10, 2006, 03:51:46 AM »
Thanks for the tips. My main goal is to get an accurate sense of when the air close to the surface freezes. The second purpose would be to have a pseudo-solar sensor that shows the solar heating during bright sunny days, although I would sacrifice that if the freeze sensing was more accurate.

I'm not sure if I need to protect it from moisture or if I need to sense the evaporative cooling when the ground gets wet.

Maybe I attach it to a heat sink, painted to match the reflectivity of the soil, then invert the heat sink with the fingers into the surface of the soil.

-David Broberg   CWOP#: CW5670 / CoCoRaHS #CO-BO-218

 

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