An ultraviolet meter is a measuring device which is sensitive to ultraviolet light. Many UV meters come with a range of sensitivities, depending on the settings where they are intended to be used. Scientific supply companies and outdoor suppliers sell ultraviolet meters, and they are also available directly through manufacturers. Sometimes they are also available at safety seminars in which health officials provide information about ultraviolet exposure, and in some cases they may even be handed out for free to the public.
One use for an ultraviolet meter is in the measurement of the amount of ultraviolet light someone is personally exposed to. People spending time outdoors, no matter what the weather is like, are at risk of UV exposure which can damage their skin and increase their risk of developing skin cancer and other skin issues. Using an ultraviolet meter, someone can determine the UV index and see how long it is safe to be outdoors. Also known as a sunlight meter, this type of meter can be extremely useful for athletes who train outdoors and people who work outdoors.
Many meters come with guides suggesting precautions to take, depending on the UV index. If the index is low, no precautions may be needed. As it gets higher, protective garments, sunscreen, and other measures may be recommended. Many personal ultraviolet meters also alert the user when the maximum level of safe exposure has been reached, allowing the user to time outdoor trips to avoid sunburn.
Another use for such meters is in climate monitoring. UV exposure varies across the Earth, and tracking programs use readings from such meters to follow trends in the climate and to identify areas of high UV exposure. An ultraviolet meter can also be used underwater, as may be done in programs which monitor reef health. These meters typically keep data logs and can send data remotely or be hooked up to a computer to offload their data for the purpose of analysis.
For people who use ultraviolet sterilization systems, an ultraviolet meter is a useful tool to monitor the system. The meter shows whether or not the exposure is consistent, and can be used to confirm that the system is functioning properly. These systems tend to become less effective with time, and it's important to know when the UV exposure is declining to the point that replacing the light bulb in the system becomes necessary. Such meters are usually waterproof so that they can be used in wet or humid environments such as fish tanks.