UVA, UVB & UVC radiometerThis is instrument cannot directly measure the UV index because it does not have the appropriate E (erythemal action spectrum), however an estimation of the current UVI can be determined by multiplying the UVB reading in mW/cm2 by 189. (Note: this instrument reads in mW/cm2... so the reading needs to be multiplied by 10 BEFORE the 18.9 factor is used below!). (This is with 10% for all for all solar zenith angles less that 70Deg)
The following is a quote from the page:
" Richard McKenzie, Dan Smale and Michael Kotkamp We discuss the move from reporting damaging UV radiation in terms of UVB to the now widely accepted erythemally weighted UV radiation (UVEry) and the UV Index (UVI). The relationship between these quantities is given: to a good approximation, it is found that UVB280–315 nm= 7.55 × UVEry. In terms of the UV Index, the estimated UVB280–315 nm in units of W m–2 is 18.9 times the UVI. These approximations generally hold to within  10% for all solar zenith angles (sza) less than 70°. For most practical purposes, this is a sufficient range, since for larger sza, the intensity of UVB is less than 10% of that for overhead sun conditions. The simple relationship above is verified using spectral measurements. "
| 