Solutions for UV Light Measurement




  Why Measure UV

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1. What is UV?

Electro magnetic radiation is emitted from the sun. This comprises of (going from long to short wavelengths) radio waves, microwaves, infra-red (or heat), visible (or light), UV, X-ray and Gamma rays. Ultra-violet radiation (UV for short) is the part of the electro magnetic radiation spectrum below visible light. That is, the wavelengths 180nm to 400nm.

UV has been classified by scientists according to the effect it has on living organisms as UVA, UVB and UVC.

UVA has the longest wavelength and starts at 315 nm (or 320 nm if you are American) and includes 400nm which is also where visible light (blue) starts. UVA is able to penetrate our skin or any substrate (such as coatings, paper etc) and is often used for "depth of cure" in industrial processes. Our skin has developed mechanisms to cope with UVA and is therefore not too harmful so long as the dose is no higher than you would get from the sun. However, it is worth bearing in mind that UVA Ages the skin.

UVB is defined as 280 - 315 nm (or 320nm if you are American). Having a higher energy than UVA, UVB does not penetrate so deep but can cure quicker. Our skin is not well protected from UVB as only small amounts penetrate the ozone layer. UVB Burns.

UVC is defined as below 240nm - 280 nm. This UV has very high energy, which it loses as soon as it hits a surface. Thus in industry UVC is used for surface cure. Life on earth has no protection from UVC and so it is highly dangerous. Therefore UVC is used for germicidal applications too as it will actually kill viruses and bacteria.

2. Why Measure UV?

The need to measure UV varies according to your application but one residing common feature is true for all - if you donít know the wavelength and intensity of the UV source, how can you be sure that the process is going to work in the predicted manner? This applies to everything from sunlamps (where you want your client to tan but not burn), to the print shop (where the printer needs to know that his inks will fully cure and not remain sticky) or germicidal applications where you need to know that the wavelength and intensity is sufficient to kill the organism targeted.
Why is it important to know the wavelength and intensity - surely if the process works and the lamp is glowing there can be no problem? Perhaps so, but who would cook a cake without checking the temperature of the oven and the length of time required for cooking? In these days of monitoring and double check it amazes us how many people are happy to run a UV process without monitoring the UV.

3. Who measures UV?

In industrial processes where UV is used to cure (or dry) a material such as ink or polymers, different wavelengths are important to the cure process for different reasons. For instance, short wavelength UV (below 280nm) is necessary for the surface cure of inks and coatings and the long wavelength UV (around 365nm) is necessary for depth of cure. Unfortunately the short wavelengths are usually the first to suffer in a process as they are easily absorbed by dirt on the lamps or reflectors. This dirt is often not visible to the eye and without measuring, it is not until surface cure is lost on a print run that the operator becomes aware that there is a problem. Watching the ratio of "short" to "long" wavelength power using the simple ratio function on the Sola-Scope or Sola-Check prior to a run will give early warning of a potential problem. Only a spectroradiometer such as the Sola Scope can do this.

A Tanning Saloon owner would want to use the Sola-Sure to test that the sunbed is both within safe limits for his customer but also intense enough to keep his customer nicely tanned.

If however you work on formulating new UV cured processes then working "blind" by trial and error is very time consuming. Taking measurements of the UV source and absorption spectra can cut research time down significantly.

Hopefully our website can help you choose a suitable instrument to match your needs. If not please contact us or your nearest distributor or agent and we will be happy to help.

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