| Spectral Region | Bandwidth (nm) | Natural Radiation (% of total) | Tolerance (% of total) | Irradiance (W/m²) | Spectral Region Irradiance (W/m²) | |
|---|---|---|---|---|---|---|
| Min | Max | |||||
| Ultraviolet - B | 280-320 | 0.5 | 0.3 | 0.7 | 5.6 | 5.6 |
| Ultraviolet - A | 320-360 | 2.4 | 1.8 | 3 | 26.9 | 62.7 |
| 360-400 | 3.2 | 2.4 | 4.4 | 35.8 | ||
| Visible | 400-520 | 17.9 | 16.1 | 19.7 | 200.5 | 580.2 |
| 520-640 | 16.6 | 14.9 | 18.3 | 185.9 | ||
| 640-800 | 17.3 | 12.8 | 19 | 193.8 | ||
| Infrared | 800-3000 | 42.1 | 33.7 | 50.5 | 471.5 | 471.5 |
| Totals | 1120 | 1120 | ||||
NOTE: The amount of radiation wavelength shorter than 300 nm reaching the Earth's surface is small but the effect on the degradation of material can be significant. Short wavelength energy below 300 nm can cause materials to fail unnecessarily (if not present in the natural exposure). In reverse, if energy below 300 nm is present in the natural environment and not present in the accelerated exposure, material that should fail may pass the test. This is entirely material dependent because it relates to the end use in natural exposure. Values in the above table have been taken from DIN 75220. (See Annex A, paragraph 2.2.)
505.7 -II. Test parameter tolerances
| Test Parameter | Description | Tolerance |
|---|---|---|
| Total Spectral Irradiance | Sum of energy for all spectral bandwidths at a target irradiance level on the test profile (diurnal curve or constant irradiance). | ±4 percent or ±15 W/m² (whichever is greater) of the target irradiance. |
| Spectral energy Distribution | Energy within each spectral bandwidth at a single measurement point. | See Table 505.7-I tolerance for each bandwidth. |
| Irradiance Uniformity | Deviation between the measured and target irradiance at all measurement points on the target plane. The number of points shall be adequate to define irradiance variation across the target plane(s) to meet the specific test requirement. | ±10 percent deviation from the target irradiance |
| Instrumentation | Pyranometer, pyrheliometer, or radiometer | See Annex B |
| Temperature | Chamber control | ±2 °C (±3.6 °F) |
| Air Speed | Across the test item | 1.5 to 3.0 m/sec (300 to 600 ft/min) |
Note: When performing Procedure I, it is not required to provide a total irradiance energy level below a minimum level of 55 W/m² (280-3000 nm). If the diurnal curve calculated energy value is below 55 W/m² (280-3000 nm), a target value of 55 W/m² (280-3000 nm) may be used for the specified time period.
- c. Calibration of chamber. Because of the variety of permissible lamps and chamber designs, it is particularly important that the chamber be calibrated to assure the proper levels of radiant infrared energy are impacting the test area when heat alone is of concern, and that the proper intensity and spectral distribution of solar radiation are impacting the test area when actinic effects are of concern. See Table 505.7-I for spectral distribution and permitted tolerances.
If the test item is not available at the time the chamber is being calibrated, ensure the radiation uniformity is within 10 percent of the desired value when measured over the area covered by the test item, at a horizontal reference plane at the approximate elevation of the upper surface position of the test item. If the test item is available at the time the chamber is being calibrated, ensure the radiation uniformity is within 10 percent of the desired value when measured over the upper surface of the test item. As most types of lamps age, their spectral outputs change. To ensure that solar radiation chambers meet established specifications, perform a thorough check on spectral distribution, intensity, and uniformity at intervals not exceeding 500 hours of operation. Conduct a check of the overall intensity and uniformity before and after every test.
- d. Record chamber temperature, solar radiation intensity, spectral distribution, wind speed, and humidity (if required) at a sufficient rate to capture data necessary for post-test analysis (see Part One, paragraph 5.18).