Hi. Morty here again. I’m thinking of buying a Davis VP pro 2 station & am wondering what the difference is between standard & fan aspirsted radiation shields are? Is it to do with accurate temperature measures? Regards Morty.
The difference between a standard radiation shield and a fan aspirated radiation shield is quite simple. The SRS just shields (in the shade) the temp/hum sensor from the sun. The FARS is the same thing, except it has a fan running 24 hours (if you have the 24 hour FARS) or a fan just running during the daytime (daytime FARS). Good luck.
–Tim
A FARS system (with the fan) will circulate the air so that it doesn’t develop a heat pocket and provide invalid results.
This is used especially in areas that get a lot of direct hot sunlight like here in Arizona. Without a FARS unit, on a still air days where it gets hot, the air inside the probe area would get hotter than the ambient temperature.
Kevin hit it right on the head.
I’m pretty sure Morty lives in AU, so I don’t necessarily know if he will need a FARS unit, probably just a SRS.
–Tim
[quote author=aifan27 link=topic=10041.msg73907#msg73907 date=1121121785]
Kevin hit it right on the head.
Center of AU is hotter than AZ.
Hi Morty,
I went for a fan aspirated radiation sheild, I previously had had a groweather station with just the standard radiation sheild and I was’nt especially happy with it during the peak of summer. This one now I am quite happy with. I do data QC checks frequently with other observation stations, and comparisons with a WMII located not far away, run by a friend (standard radiation sheild), I am quite happy with mine, and given your in Toowoomba I would think it a necessity.
Cheers
Geoff
[quote author=nikoshepherd link=topic=10041.msg73920#msg73920 date=1121123903]
I guess you never studied or checked on the climate in Australia?
Morty here Again. Thanks for all your replys. It has been very helpful. 
Even here in Scotland using a WMR928N, I find that I am developing a warm air pocket in my home made Stevenson screen. Just bought a solar panel and computer fan and in the process of sorting it out so that when the screen is in direct sunlight the fan aspirates the area around the sensor.
Kojack
Just bought a solar panel and computer fan and in the process of sorting it out
I would be interested in knowing how you get on with this, particularly in how you stop water getting into the fan. I would like to do this with a VP ISS. I have a spare processor fan, do you think this would be OK?
