The xenon aging tester uses a feedback loop control system to compensate for this. With this system, the operator presets the irradiance level and an irradiance sensor in the test chamber measures the light. The system automatically compensates by increasing the power of the xenon lamp as the output decreases due to lamp aging.
The output of any type of xenon lamp will decay over time. In advanced theory, light intensity can be monitored anywhere in the xenon lamp spectrum, but by using only a few bands. Irradiance control is generally performed in areas of the spectrum where the material is sensitive (e.g., areas where degradation is expected). In addition, irradiance control points change depending on the industry and application.
Flat panel and rotary drum test chambers are typically equipped with 340nm or 420nm narrow band irradiance control systems. Depending on the model. Some European test chambers can use a broadband TUV (complete UV, 300 to 400nm), or a very broadband complete irradiance sensor (280 to 800nm). Broadband sensors do not respond to relatively small changes in UV light, and this non-sensitivity can cause problems for critical degradation mechanisms driven by the short-wave UV portion of the spectrum.
The output of any one xenon lamp tube will decay over time. The xenon aging tester uses a feedback loop control system to compensate for this. This system allows the operator to preset irradiance levels and use radiation sensors in the test chamber to measure the light. Automatic compensation is achieved by increasing the xenon lamp power when aging causes the light source output to decay.
Theoretically, light intensity can be monitored anywhere in the xenon lamp spectrum, but only through a few bars. The irradiance is usually in the region of the spectrum where the material is sensitive (e.g., areas where degradation is expected to occur). Also, the radiation control point varies with the industry and application.
The 340nm transistor is widely used for accelerated aging tests, and for aging tests of durable outdoor products, the short-wave UV band is considered hazardous. This 340nm chip needs to be equipped with a UV sensor that can pass within a narrow band of 340nm. It is generally an ideal control point for coatings, plastics, roofing materials, etc. Commonly used radiation control points are 0.35 or 0.55 W/m/nm @ 340nm.
The 420nm control point is usually used with window glass filters for indoor light stability testing of materials. To control 420nm, the UV sensor needs to be equipped with a filter that can only pass in the middle of 420nm. The objects tested by such systems are usually damage caused by long-wave UV and visual light. For example, knitted products, paper, ink, etc. Commonly used indoor radiation radiation set point is 1.10W/㎡/nm@420nm.
420nm control points are generally used with window glass filters for indoor light stability testing of materials. The control of 420nm requires the UV sensor to be equipped with a filter that allows only a narrow band of UV light centered at 420nm to pass through. The system tests, typically, these materials that are primarily damaged by long-wave UV and visible light. Examples include fuels and pigments in knitwear, paper and ink. A common irradiance set point for indoor simulations is 1.10W/㎡/nm @ 420nm.
In summary, flat panel and rotating drum xenon aging chambers have efficient, equal-weight feedback loop irradiance control systems. It is recommended that periodic lamp replacement will reduce the effects of lamp aging. By using a sensor that controls irradiance at 340nm or 420nm, the amount of spectral change in a given area is further reduced.