Shielding temperature sensor from sun

[h2005__uk__]

I used to have my temperature sensor behind a tree but it was too shaded. I recently made a box for it based on a design I found online, then positioned the box further from the tree. The box now has sun shining on it during the afternoon. However sunlight was getting in through the holes and hitting the sensor, so I fixed  plastic louvres on the box - see below.

 

 

 

It's a bit better now but I still see artificial spikes (by up to 1C) when the sun hits the box. Would it be best to put another shield on the sensor (such as the possible ones shown below), or would this just add to the number of surfaces being warmed up? Would painting the inside of the box black be of  any  use?

 

 

 

Note: the above additional shields are from other sensors I've had, and they're not good enough to use standalone!

 

Thanks in advance

[reef]

The shields on those stations (Watson and Lacrosse I believe) actually serve more as heat traps than shields. They tend to increase the thermal mass and cause lag times during calm nights aswell.

 

For more accurate readings I would run the sensor naked inside the main shield and look at adding a FARS system somehow. I've done similar with an 80mm PC fan in my Davis VP2 as I wasn't happy with the airflow or reliability of the standard Davis fan. I've hooked mine up to the mains using a 2 wire cable and standard 12v DC adaptor and have had excellent results. I used a bit of plastic sheeting to create a shim, sat the fan in and sealed it with strong tape. Its not neat but it does the job:

 

 

(above is pre-sealing)

 

Perhaps you could do something similar at the bottom of your shield?

[Mapantz]

Similar to reef, I used a PC fan and wired it up to a mains adapter. I also painted the inside of the box black.

[h2005__uk__]

The fan is an interesting solution! I assume it's arranged so that the fan blows air out of the shield, so that air is pulled over the sensor rather than being blown onto it? Does this ensure any heat produced by the fan doesn't affect the sensor?

[4wd]

http://nymweather.blogspot.co.uk/2014/09/daytime-fars-fitted-to-vp2.html

I've just done this to my VP2.

[reef]

The fan is an interesting solution! I assume it's arranged so that the fan blows air out of the shield, so that air is pulled over the sensor rather than being blown onto it? Does this ensure any heat produced by the fan doesn't affect the sensor?

Yes, always pulling through for that very reason.

[reef]

http://nymweather.blogspot.co.uk/2014/09/daytime-fars-fitted-to-vp2.html

I've just done this to my VP2.

The daytime FARS is a nice addition but like the 24hr FARS shield the issue is that when the fan isnt running the thermal lag is quite noticeable, especially when conditions are calm. I went for dc powered for that reason and switched from the Davis fans to an 80mm PC fan as the Davis units were unreliable - I went through three in 10 months!

[TonyH]

If I could afford it I would get a MO spec Stevenson Screen again but you need a grand or two!