I finally found the time to test my 3 Arcadia 12% bulbs and 4 of the Agromax pureUV bulbs(75% UVB).
At 10" the UV checker reading was only 1,2 with the Arcadia 12% bulb and at 6" it was 2,2. This bulb was ~800h old(two runs)
A 420h old bulb reached already 2,4 at 6" and a new one has stabilized at 2,5. (takes ~1-2 minutes) According to the UV-guide.uk tests(same bulb, 100h old) it should be 5,5 and 10.1 UVI at 6". That's a huge difference...
For the Agromax bulbs it was 3,4, 3,5, and 3,4 with 3 new bulbs at 6" and an almost 140h old bulb measured still 3,3.
At 10" is was 2,4-2,5 and the used one stabilized at 2,3.
Both values are much lower then expected. I've tested them with an alli wing reflector but the readings are even lower as the results for a bare bulb. At least the Agromax bulb should be much stronger; 5 times stronger actually not only ~50%.
Pretty sure that's because all wavelength above 295nm are weighted the same. The checker can simply not distinguish between 280 and 290nm.
But why there is such a big difference to the Arcadia test results?
Probably these sensors are simply not made for artificial UV light and are calibrated to the suns spectrum. The description says the sensor can measure 240-380nm but when all below 295nm are weighted with 1.0 it would show the same results even when the Agromax wavelengths would be in the UVC range.
Even if you use the Agro's at 10" you can use them only for minutes while the Arcadia bulbs can literally run all day long at 6" without causing a serious damage. Both are 24w bulbs but the Agromax goes down below 280nm while the Arcadias have nothing below 295nm.
So IMO we can use the UV checker like a smartphone lux meter app to set up and check an even UV distribution but the measured values are almost useless and say nothing about the wavelengths or how strong the UVB light really is for plants.
Is that worth 25 bucks? Probably not!
Here are a few screenies..
For better more accurate UVI readings we need a better UVI meter like the Solarmeter one (199$)but to really make a statement about the strength of a UV bulb and its spectrum its neccessary to use a UV spectrometer.
