​​What is the LM-79 Test Methodology?

LM-79 specifies the testing processes and precautions for LED product testing, including laboratory considerations, ambient conditions, electrical equipment, and measuring equipment. Measurements are taken using either an Integrating Sphere or a Goniophotometer device. Proper orientation/test position and luminaria stability are critical for achieving reliable findings.

​​Why do we need it?

Because of the variety of LED products on the market, there is a need to analyze their quality on a level playing field and objectively evaluate different factors related to lighting products. The LM-79 test includes a wide range of factors related to the electrical, photometric, and color properties of luminaries.

How does the LM-79 test differ from other techniques of testing that are typically utilized for conventional lighting products?

Because of the unique thermal and electrical properties of LED luminaries, typical test methods based on relative photometry are inapplicable to LED light sources. The LM-79 test solves this difficulty by employing absolute photometry.

​​Applicability

 ➤ It applies to LED-based solid state lighting (SSL) products with integrated control electronics and heat sinks, i.e., devices that require just AC main power or a DC voltage power source to function.

 ➤ Luminaries SSL products in the form of luminaries (light fixtures with integrated light sources) are covered by LM-79 testing.

 ➤ This standard specifies the techniques for testing particular SSL products.

 ➤ It does not cover SSL products that require external operating circuits and external heat sinks, such as LED chips, LED packages, and LED modules.

 ➤ This document does not include the fixtures that were built for SSL items that were sold without a light source, nor does it discuss the product's performance rating.

Relative Photometry

 ➤ Relative photometry is used to examine conventional filament or gas discharge lights.

 ➤ Lamps and ballasts are evaluated independently from luminaries.

 ➤ The luminaire efficiency is computed by dividing the total lumen output of the luminaire by the product of the rated output of the lights and the ballast factor.

 ➤ Relative photometry decreases the number of luminaire tests since the specifier may imitate lamp data from current tests.

Absolute Photometry

 ➤ Absolute photometry measures the overall lumen output of whole lighting systems, including bulbs, ballasts, drivers, thermal management, and all other fixture components.

 ➤ An integrated LED luminaire's efficiency is not calculated in a conventional way.

 ➤ Instead, luminous effectiveness is evaluated by dividing total light output by the entire electrical power input.

LM-79 test outcomes

To show the results received after LM-79 testing, IESNA recommends the following consistent criteria.

​​Limitations

 ➤ The specifications of particular items are specified in LM-79, and the test results acquired cannot be used to assess related products or perform lighting calculations.

 ➤ The LM-79 does not specify a sample size.

 ➤ When the number of samples to be evaluated is not specified, producers provide only one sample rather than numerous, which increases the susceptibility of lower quality items.

​​Further Development

 ➤ Yes, the luminaries are tested within the lab under certain conditions.

 ➤ The specifications alter as soon as the product is put into the field.

 ➤ The performance of each or every component of the LED luminaire might be affected by even minor differences in operating circumstances.

 ➤ Lighting businesses are constantly striving to provide the most realistic outcomes possible.

 ➤ However, because LED lighting technologies are growing at such a rapid rate, LM-79 has already been changed in 2019 and may continue to be altered or become outdated as measuring methodologies and lighting technology evolve.