Which Solarmeter Radiometer is most useful ?

I'm thinking if buying a Solarmeter Radiometer , looking at maybe the Solarmeter 6.2 UVB as being the most useful for monitoring the performance of my UV lighting.

Or perhaps a Solarmeter 5.7 UVA/UVB Radiometer uW range might be more useful.

The 6.5 model is calibrated in UVI and this is not really suitable IMO as it's biased basis is naked human skin's response to UV.

If you were buying a Solarmeter , which ONE would you choose ?

The 6.5 is the most useful. Human skin responce is considered to be a close analog since the active range of UVB wavelengths are similar for reptiles. Other broadband meters have wider "vision" and make comparing different lamps/sunlight impossible and won't give a real description of the "strength" of the lamp relative to d3 synthesis. Also since the 6.2 sensor isn't sensitive specifically the the biologically active region so you cannot compair readings from different lamps or sunlight. It's useful really just for measuring decay. The 5.7 has an even wider responce window and would give an even less accurate idea of output.

http://www.uvguide.co.uk/usinguvmeter.htm
http://startortoises.net/uvb-readings.html

I'm more interested in monitoring UV lamp performance decay in terms of microW UVA and UVB / sq cm at a "standardised distance from the lamp front surface"
over time than VitD / sunburn potential and can not afford (at the moment) to buy 2 different Solarmeter Radiometers.

I'll have to do a bit more of a metasearch on how well lizard (bearded dragon and skink) skin corresponds to human skin in absorbing UV(B). I know even amongst humans there are differences in how well the skin does this (some people have darker skins than others).

If all you are looking for is a direct measure of emmisivity for each light to monitor decay than a 6.4 would work fine. You wouldn't be able to compare say, a tube light vs an MVB or the sun though. I don't recal if you can accurately use it to measure a bulb that's been used either, since UVA and UVB production from lamps decay at different rates. It's also possible to have high emmisivity in bulbs that don't produce a lot (relatively) of useful UVB. Anyway. Since the broadband meters aren't weighted the numerical output is not super useful and doesn't dilineate between UVA and UVB which have very different roles. For the cost of the meters and the practicality of the information they give, a 6.5 is more useful for most keepers.

Absorption vs responce wavelength isn't quite the same. If course factors like melanin and skin properties effect the amount of UV that is utilized the portion of the solar spectrum responsible for D3 action is similar.

Check out the links I posted and join up at the UV Meters group on Yahoo! Or the reptile lighting group on Facebook. Dr. Fran Baines is a contributed to both and a leading researcher in UV provision for captive reptiles. There is a lot of good info and I'm sure they can direct you to the latest research.

I think that Multipurpose environment activity radiometer RKG-14 (you can check it on ecotestgroup.com website ) is one of the best radiometers on the market. It detects and precisely measures radiation just in a few seconds. This device works effectively with Android smartphones. As far as I know, it can be used for both personal and scientific experiments.