A Snapshot Of 118 Solid State Lighting Testing Laboratories' Capabilities

The National Institute of Standards and Technology (NIST) began to offer proficiency testing for solid state lighting (SSL) products through a Measurement Assurance Program (MAP) in 2010. The MAP program provided proficiency testing complimenting laboratory accreditation to ensure that as SSL products became more prevalent, capable testing laboratories would be available to handle the volume of measurement work. This article communicates the results of the first version of the MAP in which 118 worldwide laboratories participated. The results of the comparison provide a snapshot of the capabilities of accredited laboratories worldwide. Statistical analysis of how the laboratories' measurements compared to NIST's measurements for photometric, colorimetric, and electrical quantities and fit parameters for each measurement are presented. In general, all of the laboratory results are within +/- 4% for total luminous flux and luminous efficacy measurements. The discussion provides reasons for any discrepancies or large uncertainty intervals found in the data. For example, a major finding was that measured differences of Root Mean Square (RMS) current had a larger standard deviation and number of outliers than expected. Two possible explanations are (1) the discrepancies are due to issues with using four-pole sockets and (2) the large deviation is caused by some solid state lamps being sensitive to impedance and slew rate of AC power supplies. Further research in this area is being conducted by NIST to help the testing community reach more consistent measurement results.