ANSI IESNA RP 27.2:2000 pdf free download – Recommended Practice for Photobiological Safety for Lamps and Lamp Systems-Measurement Techniques
4.1 Lamp Seasoning
To maintain stable output during the measurement process and provide reproducible results, lamps shall be seasoned for an appropriate period of time. During the initial period of operation a lamp will change as its components come to equilibrium. If measurements are taken of an unseasoned lamp, the variations with- in the measurement period and between measure- ments will be significant. As the output of a lamp gen- erally decreases over life, the seasoning time should be short to result in conservative hazard evaluations. Seasoning of lamps shall be done as stated in IESNA LM-54. For the purposes of these standards, the lamp output at the end of the seasoning period is the initial output. For lamps not covered by the LM-54 standard, a study may be required to find the minimum time required to stabilize the operation of a source.
4.2 Test Environment
Measurements shall be made in a controlled environ- ment. The operation of sources and measurement equipment is impacted by environmental factors. Additionally, the formation of ozone in the measure- ment path may compromise accuracy and may pre- sent a safety hazard.
4.3 Temperature
The ambient temperature will significantly influence the output of certain light sources; e.g., fluorescent lamps. The ambient temperature in which measure- ments are taken shall be maintained in accordance with the appropriate IESNA LMs noted in Section 3.1.
4.4 Drafts
The characteristics of some light sources are signifi- cantly affected by drafts. For the applicable light source, refer to the appropriate IESNA LM guides noted in Section 3.1. Other than normal convection air, air movement over the surface of test lamps should be reduced as much as possible consistent with safety considerations (ozone production). When the system under test provides interlocks that maintain circulation, measurements shall be performed with circulation.
The measurement of a source for the purpose of haz- ard classification requires accuracy during calibration and testing. The detector‘s broad spectral response and high spectral resolution required to provide accu- rate weighting leads to stringent requirements for out- of-band stray light rejection. Calibration sources pro- vide wide spectral output, which needs to be rejected out of the pass-band. The ratio of out-of-band energy to pass-band energy at 270 nm for tungsten halogen incandescent calibration lamps (e.g., the FEL) is >1. The double monochromator is the only instrument that provides the needed selectivity, and it is recommend- ed for hazard measurements involving UV and visible radiation. It is recognized that monochromator sys- tems introduce limitations in convenience and speed.
A monochromator with perfect triangular spectral response used in a system that has a reporting inter- val that divides into the bandwidth integrally will accu- rately measure all signals regardless of their spectral shape. (See CIE 63, Section 1.8.4.2.1 or Koctkowski 1997, Section 5.9.) Deviations from this may lead to errors in measured energy. The spectral response of the system is determined by a spectral scan of a nar- row isolated spectral line, e.g., filtered laser or atomic emission, using scan steps much smaller than the instrument’s bandwidth. The resulting spectrum is a mirror image of the system’s spectral response. The spectral response is what would be found by holding the instrument at a single wavelength and noting the response to a monochromatic source whose wave- length is varied around the that wavelength. (See Kostkowski 1997, Section 4.9.) The system’s ability to accurately measure the energy in a narrow band sig- nal is the sum of the spectral responses at each reported wavelength. The variation across the summed spectrum is the potential error in total mea- sured signal and shall be included in the uncertainty analysis.