LM79,LM80_Understanding
Understanding IES LM-79 &
IES LM-80
Eric Richman
Pacific Northwest National Laboratory
LightFair Exhibit
May 5-7, 2009
IES LM-79
“Electrical and Photometric Measurements of
Solid-State Lighting Products”
• Approved method describing
procedures and...
Understanding IES LM-79 &
IES LM-80
Eric Richman
Pacific Northwest National Laboratory
LightFair Exhibit
May 5-7, 2009
IES LM-79
“Electrical and Photometric Measurements of
Solid-State Lighting Products”
• Approved method describing
procedures and precautions
in performing reproducible
measurements of LEDs:
– total flux,
– electrical power,
– efficacy (lm/watt), and
– chromaticity
LM-79 Scope
• Applies to LED-based products incorporating
control electronics and heat sinks:
– Products requiring only line voltage or DC power
supply
– Includes complete LED luminaires and
– Integrated LED sources (LED chips with heat sinks)
• Does not cover
– LED products requiring external operating circuits or
heat sinks (bare LED chips, pkgs, and modules)
– Fixtures designed for LED products but sold without a
light source
Absolute Photometry Basis
• LM-79 requires complete luminaire testing
• Traditionally, photometric evaluation of
lighting products is based on separate
tests for lamps and luminaires (“relative”)
• For SSL products, LED lamps typically
cannot be separated from their luminaire
because of heat effects (“absolute”)
Relative vs. Absolute
Photometry
• Relative testing
– Lamps of interest and luminaire (with reference lamp)
are measured separately. Then the actual light
distribution and intensity of the complete luminaire of
interest is derived by normalization of the test data
• Absolute testing
– The actual light distribution and intensity of the
luminaire of interest is measured directly from the
complete luminaire
Procedures/Conditions
• Ambient conditions
– Temperature – maintain at 25C +/-1C (within 1m)
– Mounting – limit thermal transfer
– Air flow - limited
• Power Supply characteristics
– AC waveshape limit to harmonic RMS of 3%
– Voltage regulation to +/- 2%
• Seasoning and stabilization
• Testing orientation
• Electrical settings
• Instrumentation
Test Methods: Integrating
Sphere System
(a) Setup for all types of SSL products
(b) Setup for SSL products with only forward emission
or
Photometer
or
Photometer
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)
Test Methods:
Goniophotometer System
For measuring luminous
Intensity Distribution
•Total Luminous Flux is
derived
•Provides color
characteristics with
Spectral radiometer
including CCT, CRI
Test Outputs/Calculations
• Total Luminous Flux
• Luminous Intensity Distribution
• Electrical Power
• Luminous Efficacy (calculation)
• Color Characteristics
– Chromaticity
– CCT
– CRI
IES LM-80
“Measuring Lumen Maintenance of LED Light
Sources”
• Approved method for
measuring lumen depreciation
of solid-state (LED) light
sources, arrays and modules
• Does not cover measurement
of luminaires.
• Does not define or provide
methods for estimation of life.
What is “Life” for Lighting?
• “Operational failure”
– Most light sources
“burn out” (End of “Life”)
– Lamp life is typically
rated at 50% failure rate
– LEDs typically don’t fail
(no filament to “burn”)
“Life” for LEDs
• Useful light output (Lumen Maintenance)
– All light sources degrade but most just “burn
out” before serious loss of light output
– LEDs continue to degrade – eventually
beyond useful light output
Source: Lighting Research Center - Rea 2000; Bullough 2003
Procedures/Conditions
• Ambient conditions and setup
– Case Temperature measured and maintained
– Case Temperature measurement point
– Airflow minimized
– Operating orientation & spacing per manufacturer
• Electrical
– Voltage and Current (AC or DC levels)
– Voltage waveshape (harmonic distortion <3%)
– Current Regulation
• Instrumentation
Measurement Methods
• Case Temperatures
– Measurement performed at multiple temperatures to
address in-situ conditions
– 55C, 85C and 3rd manufacturer selected temperature
• Photometry
– Spectral radiometer preferred method
– Temperature: 25C ambient
– Drive current per manufacturer
• Testing Intervals
– 6000 hours min testing period. 10K preferred.
– Minimum at least every 1000 hours
Testing Output and Use
• Test report basics
– Description of Sources tested
– Ambient conditions (Airflow,
temperature, RH etc)
– Case Test point temperature
– Electrical conditions
– Lumen maintenance data
– Observation of failures
– LED monitoring interval
– Chromaticity shift over time
LM-80 provides no determination or
estimation of expected life or lumen
output beyond test data.
Separate estimation method (TM-21) is
in development
Understanding IES LM-79 & IES LM-80
IES LM-79�“Electrical and Photometric Measurements of Solid-State Lighting Products”
LM-79 Scope
Absolute Photometry Basis
Relative vs. Absolute �Photometry
Procedures/Conditions
Test Methods: Integrating� Sphere System
Test Methods: �Goniophotometer System
Test Outputs/Calculations
IES LM-80�“Measuring Lumen Maintenance of LED Light Sources”
What is “Life” for Lighting?
“Life” for LEDs
Procedures/Conditions
Measurement Methods
Testing Output and Use
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