Measuring UV Radiation

Ultraviolet light refers to the wavelength of the electromagnetic spectrum from 100 nm to 400 nm and cannot be perceived by the naked eye. UV radiation is divided into three radiation wavelength bands: UV-A, UV-B and UV-C

UV-A is a long-wave UV-transparent radiation, wavelength 315 nm - 400 nm, which can make the skin elastic and collagen fibres can make the skin tan. 

UV-B is a medium-wave ultraviolet ray with erythema effect to promote mineral metabolism and vitamin D formation in the body. The wavelength is 280 nm - 315 nm, but long-term exposure is not recommended, as erythema peeling will cause tanning of the skin. 

UV-C is a short-wave ultraviolet ray that has a bactericidal effect. The wavelength is 200 nm – 280 nm. The UV-C wavelength is very harmful to the human body. Short-term exposure can burn the skin. If it is exposed for a long time, it will cause skin cancer. 

Ultraviolet rays are often used in our lives. UV-C radiation is often used in hospital germicidal lamps. UV-B radiation is often used in health care physiotherapy lamps. UV-A radiation is often used in curing lamps in the curing industry.  


Generally, the intensity and energy of ultraviolet light are detected. It is recommended to use an ultraviolet radiation meter (UV meter) with a suitable probe. 

How to measure UV Lamp Output Radiation 

The irradiance of UV lamps can be measured with specially designed optical measurement probes. The measurement probe is usually connected via cable to the measuring device. The inverse square law dictates the UV radiation (same as visible light). In principle, the signal reduces as the distance from the source increases. In practice, the further from the UV source, the smaller the signal level obtained. Therefore, a certain distance from the lamp needs to be determined to perform a measurement (most laboratory measurements are currently done with a 1 meter distance between UV lamp and detector). Additionally, we cannot forget the cosine law from physics which states the radiance power falling on a surface is a function of the cosine angle; consequently, the measurement intensity is highest when radiation is perpendicular to the sensor. Finally, depending on the UV wavelength being measured in a UV system proper performance verification is needed. This illustrates why the calibration of the measuring devices gets more challenging, since in another way,killing viruses with UV radiation is possible only when a specific radiation is penetrating the molecules, a small shift of the wavelength can impact the effectiveness of the UV measurement process.  

Last but not least – the safety consideration! 

UV radiation is harmful for all living organisms. It kills viruses, bacteria and other biomaterials and so it can damage our skin and eyes. Please remember that UV lamps cannot be used for bare skin disinfection!!!  

Also when working with UV sources, special care must be taken to provide skin and eye safety by safety glasses and clothes.