What's up guys, just thought I'd pop in and say hi.
As for the "UVI vs UV measurement" ...
The unweighted UV measurement will always be a considerable amount more than the UVI × 25mW/m2. The UVI × 25mW/m2 is only the area under the created curve, you'd have to divide the created curve by the erythemal curve and then integrate from 280nm to 320nm to be able to compare apples to apples.
The UVI curve (
*) is created by multiplying the erythemal curve (
*) by the actual radiation curve (
*, actual SPD curve) for every nm of WV from 295 to 400 (I think it's all the way to 400nm). So its multiplying the lights individual WV intensity at 295 by 100%, 296nm at 93%, 297nm at 87%, 298nm at 80% 299nm at 74%, ect ect. all the way till 400nm. It's just multiplying the actual SPD by the erythemal to create a UVI curve that's further integrated and divided by 25mW/m2 for a final UVI.
At ~309nm the erythemal weighting has already diminished to ~10% with 295nm being 100%. So if your UVB meter is reading 800μW/cm2, you have to remember that barely any of that is <296nm, and at 309nm you're only about 10% weight, let alone 1% at 319nm. The 800μW/cm2 is being recorded unweighted and the majority of that unweighted emmission recording is primarily from 320nm due to the SPD of the bulb, so the total reading should be much greater than the weighted reading.
- debilt20020601.gif (10.58 KiB) Viewed 1602 times
^^^The yellow portion is the UVI index that still needs to be divided by 25 to achieve a UVI. The area under the "measured" spectrum from 280nm to 320nm is the total quantity of UVB that your UVB meters will pick up...
Ill have to check out the video, sounds interesting.