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Handling of absolute photometry data in EULUMDATfiles

Release: August 14, 2009

SummarySSL luminaires already have a sizeable market share. In future this will evengrow. Unfortunately the SSL technology often does not enable the laboratory todo a relative photometric measurement. Often it is impossible to separate the

lamp that means the LED Chip or Cluster from the luminaire or the separationwould lead to totally wrong results. One solution to avoid these problems couldbe the usage of absolute photometry. The documentation of absolute measuredphotometric data is provided in the IESNA file format IES-LM-63.

This document describes how an EULUMDAT file can be created and interpretedto use absolute measured data instead of relative measured data. This is acommon suggestion from Ian Ashdown, Lighting Analysts and DIAL.

Motivation

The lighting industry will be unable to present relative photometric data forspecific products respectively clients from the United States and Canada will askfor absolute measured data for SSL luminaires. The widely spread data formatEULUMDAT does not offer the possibility to transfer data of absolutephotometry. To enable laboratory software and lighting design software tocontinuously use the well-established EULUMDAT format there are little changesand additions in this format necessary.

Ian Ashdown, Lighting Analysts (AGI32) and DIAL (DIALux) agreed upon acommon way to interpret EULUMDAT files that also the handling of absolutephotometry is possible. It would be beneficial for the whole lighting industry ifluminaire manufacturer, manufacturer of photometric equipment and software

manufacturer would act in a common way.

ImplementationThis document describes how to generate and interpret an EULUMDAT filecontaining absolute photometric data.Without any changes to the EULUMDAT file format specification, an EULUMDATfile representing absolute photometry can be interpreted as:Item Designation Absolute Photometry

ValueNotes

26 Number n of standard sets oflamps

1 1

26a Number of lamps n (number of light 2

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emitters)26b Type of lamps 3

26c Total luminous flux of lamps(lumens)

Luminous flux (lm) ofluminaire

4

30 Luminous intensity distribution(cd/klm)

5

Notes1. Field 26. There can be only one standard set of lamps for absolute

photometry, and the value is fixed at 1.2. Field 26a. While the number of lamps n is meaningless for absolute

photometry, it may still be useful to indicate the number of light emitters,such as the number of LEDs. The value is therefore retained, but its sign isnegative to indicate absolute photometry.

3. Field 26b. Type of lamp is just informative. It could be for example the ILCOScode for a reflector lamp, or the manufacturers name for a type of LED.

4. Field 26c. In accordance with the principles of absolute photometry, this fieldreports the measured luminous flux of the luminaire rather than the totalmanufacturers rated lumens of the lamps.

5. An advantage of this interpretation for the luminaire manufacturer is that thereported luminous flux can be measured with for example an integratingsphere rather than a goniophotometer. This makes it possible to measure oneluminaire with a goniophotometer to determine its luminous intensity

distribution, and then measure multiple identical luminaires to obtain anaverage total luminous flux value.

6. Field 30. All values are stated in candela per kilolumen (cd/klm). Theadvantage is that there is no change to the existing format.

7. This interpretation is fully compatible with existing EULUMDAT photometricdata files, and also with existing lighting design software programs as long asthey do not perform range checking on field 26a. (This is unlikely, as thenumber of lamps is not required when interpreting the luminous fluxdistribution of a luminaire.)

ImplementationGiven that no changes are required to the EULUMDAT file format specification,

support for absolute photometry can be provided immediately. Responsibilitiesfor the various parties include:1. Photometric Testing Laboratories

Use n in field 26a to designate absolute photometric data reports. (Thisis a convention only.)

2. Luminaire Manufacturers Request EULUMDAT files with n in field 26a for products requiring

absolute photometry (primarily for solid-state lighting products, but alsofor lamps and luminaires with non-removable lamps).

3. Lighting Design Software Manufacturers Modify future version of their products to indicate EULUMDAT files with

absolute photometric data.