Surveillance of Sunbeds

Monitoring the radiation of sunbeds serves two major purposes - finding out the current radiation intensity and establishing the (accumulated and biologically effective) dose the user has been exposed to. The intensity of the fluorescent lamps that are usually used as UV source decreases in time. As a consequence, a longer tanning session is needed for a particular dose. 

In modern systems, the applied electric power is increased over time to compensate for the decreasing intensity. However, this adjustment uses the average degradation curve of a lamp as a reference, not the actual values of the lamps mounted in a particular sunbed. A radiation sensor could be used to control an active circuit that regulates the intensity of radiation. 

In household heating systems running on gas or oil the presence of the flame has to be surveyed. If the flame extinguishes, a burner control system has to reignite the flame or the fuel supply has to be stopped. Several flame-sensing mechanisms are used in the control systems. 

The yellow flame of traditional oil burners is often surveyed by flame guards that react on the visible emission. More modern oil heaters use blue-burning flames. There, the carbon black of the combustion process is redirected to the combustion area for a more complete combustion, thus giving higher efficiency. With the reduced carbon black their yellow emission in the visible also vanishes, leaving an almost invisible flame, see Fig. 5.44. For these blue flames surveillance based on UV emission is preferable 

As can be seen in Fig. 5.44 as well, flames in gas heaters have a similar emission spectrum. Besides the UV surveillance ionization electrodes are often used in gas burners. The method is cheap and secure but it disturbs the combustion process since the electrode has to be placed close to the flames. New developments in gas heaters focus on catalytic combustion on a metal mesh. There, an ionization electrode would fail due to the lack of a flame. However, the characteristic UV emission is still present 

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