Occasionally, Lighting Analysts will hear from one of our customers that our software can’t read their photometrric file (IES, Eulumdat, TM14)? Why would that happen?
Lighting Analysts’ software (AGi32, ElumTools, and Photometric Toolbox) is programmed to read IES-format photometric data files that follow IES LM-63-02 protocol for reporting the data. This protocol has been in place since 2002. (The previous version was LM-63-95, from 1995.) These protocols are applied to other formats as well (Eulumdat and TM14). Sometimes when the data doesn’t follow this protocol, it’s not a big problem. Example: missing the date that the test was conducted. It’s supposed to be there, but if it isn’t the software can still use the rest of the data. However, if certain other data is flawed or missing, AGi32/ElumTools/Toolbox cannot use that photometric file.
The items that are most often problematic are:
Incomplete set of test angles. If there is missing data, the software doesn’t know what the missing values should be. It could assume all zeros, but that assumption would not be correct in all cases.
- LM-63-02 calls for luminaires to be reported for 0-90 or 0-180 degrees vertical. In other words, the last reported vertical angle should not be 85 or 175 degrees.
- LM-63-02 calls for luminaires to be reported for 0-90, 0-180, or 0-360 degrees horizontal. In other words, the last reported horizontal angle should not be 45 or 355 degrees (If the distribution is circular-symmetric, they can report just the data for the 0-degree horizontal angle only.)
Nadir (or zenith) candela angles are not all the same. In the testing lab, the nadir values (and zenith values when applicable) are measured several times during the course of a test. Due to tolerances in the lab, there can be a small difference between measurements, but the test lab should adjust the test results so that all of the nadir values (and zenith values if measured) are identical. In order to read a file with this kind of error, the software would have to either average the data or choose one of the values as the “correct” one. But which of those options would be best? The answer will vary with the file; there isn’t one method that would always be correct.
If the software rejects a photometric file, it always gives the reason. The burden is on the supplier to provide accurate data in compliance with the current standard or testing protocol, rather than expecting the software to make assumptions about the data.