QUV Ultraviolet Fluorescent Lamps
All of the QUV tester's lamps emit mainly ultraviolet rather than visible or infrared light. All are electrically equivalent to an ordinary 40-watt fluorescent. However, each lamp type differs in the total amount of UV energy emitted and in its wavelength spectrum. Fluorescent UV lamps are usually categorized as UV-A or UV-B lamps, depending on the region into which most of their output falls.
UV-A lamps are especially useful for comparing different types of polymers. Because UV-A lamps do not have any UV output below the normal solar cutoff of 295 nm, they usually do not degrade materials as fast as UV-B lamps. However, they usually provide better correlation with actual outdoor weathering.
UV-B radiation includes the shortest wavelengths of sunlight found on the earth’s surface. Consequently, fluorescent UV-B lamps are widely used in QC and R&D for fast, cost-effective results. Because all UV-B lamps emit unnatural, short-wavelengths of UV that are below the solar cutoff of 295 nm, anomalous results can occur. Two types of UV-B lamps are available. They emit different amounts of total energy, but produce the same UV wavelengths in the same relative proportions.
Q-SUN Full Spectrum Xenon Arc Lamps
Xenon arc lamps give the ultimate correlation to the full spectrum of natural sunlight. Unlike the QUV tester whose lamps directly determine the radiation that specimens see, the Q-SUN tester requires optical filters to accomplish the same. These optical filters are used to simulate a variety of service environments including direct sunlight and sunlight through window glass. Filter performance does not decline with age; therefore, filters do not need to be replaced unless the glass is broken.
The Q-SUN B02 model’s optical filter lantern is designed to produce the spectra specified in ISO and AATCC test methods and is equivalent to sunlight coming through window glass. The lantern consists of an outer borosilicate cylinder and two sets of 7 inner filters, arranged in a two-tier heptagon.
There are three general categories of filters which can be used in the Q-SUN Xe-1 and Xe-3 xenon test chambers. The choice of filter depends upon the material tested and its end-use application. Within each general category, there may be several different types of filters. Each filter is a flat piece of specialty glass specifically designed to have a particular transmission.
Because the radiation from an unfiltered xenon arc contains too much short-wave UV to allow useful correlation to natural exposures on the earth’s surface, Q-SUN testers employ various types of filters to reduce unwanted radiation and achieve an appropriate spectrum. For most of the filter types used, the greatest effect is on the short wavelength portion of the spectrum. Because the damaging effects of UV are inversely proportional to wavelength (i.e., shorter wavelengths = more damaging), it is critical that the cut-on wavelength match the service environment.
Low Cost Replacement Lamps and Filters for Atlas Weather-Ometer® Testers
Q-Lab offers water-cooled replacement lamps and optical filters for use in Atlas Weather-Ometer® models Ci35, Ci35A, Ci65,Ci65A, Ci4000, and Ci5000. These replacement lamps and filters are lower in cost and guaranteed to have a comparable spectral power distribution to those supplied by Atlas.
®Weather-Ometer is a registered trademark of Atlas Material Testing, LLC