Here makes one general introduction to three important electrical and photometric measurements of SSL products, including LM-79, LM-80 and TM-21.
IESLM-79 is one approved method that describes procedures and precautions in performing measurement of LED products.
LM-79 is applied to solid-state lighting products that include the following requirements:
---LED-based products that are integrated control circuit and heat sinks
---LED-based products only requiring AC or DC power supply
And does not cover as bellow:
---LED products requiring external operating circuits or heat sinks (bare LED chips, package and modules)
---Fixtures designed for LED products but sold without a light source
---Total Luminous Flux
---Light Intensity Distribution
---SSL products work with AC power: voltage, electrical current, power, frequency, power factor
---SSL products work with DC power: voltage, electrical current, power
1. Ambient Conditions
Temperature--maintaining at 25℃±1℃
Mounting--limited thermal transfer
2. Power Supply
Voltage regulation to ±2%
Voltage waveform (harmonic distortion< 3%)
3. Aging and Stabilization
---New SSL products can be put into tested without aging.
---Before testing, SSL products should work for a certain time to reach up stable working temperature.
4. Working Orientation
Integrating Sphere &Goniophotometer available to achieve the test report
For measuring total luminous flux and color
Photometer – Total Luminous Flux
Spectral Radiometer (preferred) - Spectral Radiant
Flux (to derive total luminous flux and color qualities)
For measuring luminous intensity distribution
Total luminous flux is derived
Provides color characteristics with spectral radiometer including CCT, CRI
Before discussing about IES LM-80, I would like to introduce two concepts: life of lamp vs life LEDs.
1. Life of Lamp
When talking about life of lamp, we mean the operation time of lamp(s). For one piece of lamp, while most light sources burn out and the lamp has ended its life. That is operational failure.Typically, lamp life is rated at 50% failure rate.
2. Life of LEDs
Life of LEDs refer to the useful light output, which is referred to lumen maintenance.
IES LM-80 is one approved method that measure lumen loss SSL light sources, arrays and module. Note that LM-80 measurement do not cover measurement of luminaires and does not define methods for life estimation.
Test report basics cover the following:
---Description of Sources tested
---Ambient conditions (Airflow, temperature, RH etc)
---Case Test point temperature
---Lumen maintenance data
---Observation of failures
---Chromaticity shift over time
---LED monitoring interval
1. Ambient Conditions
Case Temperature measured and maintained
Case Temperature measurement point
Operating orientation & space
2. Electrical Setting
Voltage and Current (AC or DC levels)
Voltage waveform (harmonic distortion <3%)
4. Testing Intervals
---6000 hours min testing period, 10K preferred
--- Minimum at least every 1000 hours
TM-21 is a technical memorandum being developed by an Illuminating Engineering Society (IES).
It is currently in the IES vote/comment stage and therefore, may change before final publication.
It is one separate estimation method to test long term luminance maintenance, which is one important supplement for LM-80.
---Adopted by organizations/programs as documentation of performance
---Program may define who does calculations( lab, manufacturer or other)
---TM-21 may be requested as part of LM-80 test
---Test lab will need to develop calculation sheet