Determining the UV Index

In the solar spectrum, the ultraviolet (UV) section has multiple positive effects but also has the potential to be highly damaging if the UV radiation goes beyond “safe” limits.

The UV Index, a parameter for UV exposures, is used to highlight UV radiation and its potential harmful effects.

Table 1 presents the calculation technique for the UV Index. As the different skin types significantly vary in their response to UV doses, various groups were created in relation to the skin’s capacity for tanning. Table 1 presents this classification.

Table 1. Classification of skin types (adopted from TB Fitzpatrick and JL Bolognia, 1995). Source: Global Solar UV Index, A Practical Guide, World Health Organisation 2002.

Classification of skin types (adopted from TB Fitzpatrick and JL Bolognia, 1995).

As displayed in Table 1, The Global Solar UV Index (UVI) was created through collaborative work by WHO along with ICNIRP, WMO and UNEP. It is a basic parameter of the level of UV radiation level at the surface of the Earth.

It can be used as an important tool to increase public knowledge of the issue and to notify the public about the requirement for protective measures to be adopted when subjected to UV radiation.

UV Radiometers

Kipp & Zonen provides UV-S-E-T precision radiometers for the quantification of the Erythemally weighted UV radiation. Furnished with quartz diffusers and domes, the radiometers offer a consistent cosine response function for precise measurements of radiative energy.

The highest degree of precision is ensured by the thermostat control of the detection system. The radiometers can be utilized in all weather conditions thanks to their rugged construction, as well as in very cold and hot locations.

An output of 0 - 3 VDC is provided by the UV-S-E-T radiometer, which translates to Erythemal radiation of 0 - 0.6 W/m². The technique demonstrated below can be used to determine the UV Index.

UV Index

The UV-Index can be calculated using the below method from UV-E radiation measurements.

In line with ISO 17166:1999/CIE S007/E-1998, the output should be taken from the UV-E radiometer. The output voltage should then be changed to W/m² with the sensitivity of the instrument.

Determining the UV Index

Image Credit: OTT HydroMet

Erythemal Action Spectrum

The UV radiometer must imitate the human skin because sunburn is an effect of excessive exposure to UV radiation. A specific Erythemal action spectrum has been created that represents the human skin’s sensitivity to UV radiation.

These particular filters, which correspond to the Erythemal action spectrum, are included in the UV-S-E-T radiometers.

This information has been sourced, reviewed and adapted from materials provided by OTT HydroMet.

For more information on this source, please visit OTT HydroMet.


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