[Robyn1973f (OP)]

I have a bearded dragon and use Arcadia T5 strip light for UV which reptiles need. The manufacturer gives information on when to replace the strip (typically 11 months for this one but some are between 6-10 months). I want to be able to check that the strip light is working effectively and providing enough UV and also be able to measure the UV at regular intervals to ensure that I replace the light when necessary. I am trying to ensure that the amount of UV never falls below the safe limit (not sure yet what that is) and that I am not replacing bulbs too early which would be uneconomical. Arcadia recommend the Solar Meter 6.2 but I wonder if there is a cheaper alternative as I have seen many for sale on eBay etc but how do I know if they will provide the right info?

Here is a link to some of the others I found on eBay: newbielink:http://www.ebay.co.uk/sch/i.html?_odkw=uv+index&_osacat=0&_from=R40&_trksid=p2045573.m570.l1313.TR0.TRC0.H0.Xuv+index+meter&_nkw=uv+index+meter&_sacat=0 [nonactive]

[RD]

There paints and plastics which change colour when exposed to UV ...
http://www.mindsetsonline.co.uk/Catalogue/ProductDetail/photochromic-pigments-uv-pigments-?productID=51f4b5dd-3e59-4561-9e41-1ec6409fd75e&catalogueLevelItemID=00000000-0000-0000-0000-000000000000

http://www.mindsetsonline.co.uk/Catalogue/ProductDetail/uv-beads-smart-beads-?productID=5bb68369-550a-45fd-ac50-f0a9f4fed308&catalogueLevelItemID=00000000-0000-0000-0000-000000000000

If the colour change is consistent they could be used to measure the amount of UV.

[Robyn1973f (OP)]

No it needs to give proper readings to be reliable but thank you for the suggestion.

[chiralSPO]

In theory, a UV diode of the right frequency connected to a multimeter would let you quantify the incident UV light of the same (or higher) frequency by measuring current. A quick google search for "UV LED" shows that they are available for <$1, making this a very cheap solution, provided you already have a multimeter (cheapest look to be about $30, but you may wish to invest in a slightly more expensive model...)

This is not a well-formed idea, just a suggested path to consider. Good luck!

[CliffordK]

I suppose the question is how you expect your UV light to fail. 

A "black light" bulb should be essentially all or none, in which case you just need some kind of a qualitative measurement.  Various white paints, paper, fabrics, and etc fluoresce under black light.  Shut off the lights and see if your paper is still fluorescing.  I think the bulbs also have somewhat of a purple glow to them, so just glancing at the bulb in a darkened room (not staring) should be enough to determine if it is working.

Quantitative measurements may only be useful for an initial configuration, and even so, there may not be experimental data to back up exact configurations. 

[evan_au]

Probably the most difficult aspect is finding a meter calibrated in the units quoted by your dragon vendor.

If you use one of the simpler numeric methods above (eg blue LED+multimeter), you can take a measurement with a new UV lamp, and then watch how the output decreases over the following months 6-11 months. Most importantly, is it a steady decline in UV output, or a sudden death?

This should give you an indication of what to look for with your next lamp.

Lizards (and dragons) have to cope with widely varying UV levels between summer and winter, or cloudy and sunny days, so they probably have a fairly wide tolerance to variation in the light output. It is probably still beneficial when the UV light output has dropped to half of the original level.