The irradiance uniformity of the QUV accelerated weathering tester is excellent -  greater than 90% over the specimen exposure area.

The irradiance uniformity can drop on the edge of the tester due to physical and geometric limitations that apply to all fluorescent UV testers.  For this reason, Q-Lab suggests regular specimen reposition.  This practice improves water spray and temperature uniformity in accelerated weathering and corrosion testers as well.

With proper installation and specimen mounting, the temperature uniformity in the QUV is also very good. It is very important, however, that you avoid leaving any gaps on the ends or between specimens. These gaps cause air to rush out of the chamber, which causes cooling on adjacent specimens and causes hot spots in other locations. 

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