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1. What is IES LM-80 Test
IES LM-80 (full name: IESNA LM-80-20) is a standard issued by the Illuminating Engineering Society (IES) of North America for measuring lumen maintenance and chromaticity retention of LED packages, light engines and luminaires. It specifies long-term aging test rules under controlled temperature and driving current to record luminous flux degradation over operating time.
LM-80 testing is the core reliability assessment for LED lifespan. Its measured data serves as the fundamental input for lifespan extrapolation via TM-21 calculation, and is a mandatory prerequisite for DLC QPL and ENERGY STAR certification applications.
Valid Standard: IESNA LM-80-20 (2020 Edition, current in force) Test Specimens: LED Packages, LED Arrays, LED Modules & LED Light Engines Minimum Mandatory Test Duration: 6,000 hours (required by DLC & ENERGY STAR)
2. Core Measured Parameters for LM-80
表格
| Parameter | Description | Test Frequency |
|---|---|---|
| Lumen Maintenance | Percentage of retained luminous flux versus initial value at specified aging time | Every 1000 hours |
| CIE Chromaticity | Variation of CIE1931(x,y) & CIE1976(u',v') chromatic coordinates during aging | Every 1000 hours |
| Case Temperature (Ts) | Substrate / enclosure temperature of LED module for aging condition control | Continuous real-time monitoring |
| Forward Current (If) | Operating driving current kept within rated specification | Continuous real-time monitoring |
| Forward Voltage (Vf) | LED forward voltage drop with slight drifting during aging | Every 1000 hours |
3. Specified Test Temperature Settings
表格
| Temperature Type | Typical Setting | Explanation |
|---|---|---|
| Low Temperature | 55°C | Simulate outdoor or low-load operating environments |
| High Temperature | 85°C | Simulate high heat dissipation scenarios: high bay, street lamp etc. |
| Application-Specific Temp | Custom-set by applicant (65°C /75°C optional) | Reflect actual in-system working temperature of end luminaires |
4. IES TM-21 Lifespan Extrapolation Introduction
IES TM-21-19 Projecting Long Term Lumen Maintenance of LED Light Sources is the statistical extrapolation standard paired with LM-80 to predict long-term LED service life based on aging data.
4.1 Definition of L & B Rating Terms
表格
| Symbol | Definition | Illustration |
|---|---|---|
| L70 | Runtime when luminous flux drops to 70% of initial value | Most widely adopted lifespan benchmark |
| L80 | Runtime when luminous flux drops to 80% of initial value | Used for high-performance application requirements |
| L90 | Runtime when luminous flux drops to 90% of initial value | Applied in museums, galleries and premium high-CRI locations |
| B50 | Median operating hour when 50% samples reach designated L rating | Median statistical reference for lifespan |
4.2 TM-21 Extrapolation Restrictions
- Single batch test: Max extrapolation = actual LM-80 test hours × 6
- ≥3 separate batches: Max extrapolation = actual LM-80 test hours × 5.5
Example: 6000h verified LM-80 data → maximum extrapolated L70 lifespan = 36,000h
5. Standard LM-80 Test Procedures
Step1 Sample Preparation: Same production batch LED packages/modules; minimum 20 specimens per single temperature condition. Step2 Zero-Hour Initial Measurement: Record baseline initial luminous flux and chromaticity for all samples. Step3 Start Continuous Aging: Run specimens under fixed Ts temperature and rated forward current up to minimum 6000 hours. Step4 Periodic Retest: Remove samples every 1000h for flux & chromaticity inspection and data logging. Step5 Data Sorting & TM-21 Calculation: Conduct exponential curve fitting per TM-21 algorithm to compute predicted L70/L80/B50 lifespan. Step6 Report Issuance: NVLAP-accredited testing laboratory issues official LM-80 test report plus separate TM-21 calculation report.
6. LM-80 Requirement for Global Certifications
表格
| Certification Program | LM-80 Mandatory | TM-21 Mandatory | Minimum Test Duration |
|---|---|---|---|
| DLC QPL Qualified Listing | Yes (NVLAP-accredited lab required) | Yes (L70 ≥54,000h mandatory) | 6000h |
| ENERGY STAR SSL | Yes (NVLAP-accredited lab required) | Yes (specified L70/L80 thresholds) | 6000h |
| DesignLights Consortium | Yes | Yes | 6000h |
| China GB/T 24823 | For reference only | For reference only | Follow domestic GB standard |
7. Frequently Asked Questions
Q: What is the difference between LM-80 and TM-21? A: LM-80 defines standardized long-term aging measurement methodology for lumen maintenance data collection; TM-21 is the mathematic extrapolation standard to predict long-term L70/L80 lifespan. LM-80 provides raw test data while TM-21 calculates projected service life.
Q: What is the minimum required LM-80 testing duration? A: Minimum mandatory aging time is 6000 hours (~250 calendar days) per IES, DLC and ENERGY STAR regulations. TM-21 extrapolation cannot exceed six times the actual verified aging hours.
Q: Can one single LM-80 report cover multiple finished lamp models? A: An LM-80 certificate is tied to a specific LED source model. If multiple luminaires adopt identical LED component with same driving current and case temperature, they may share the same LM-80 report subject to prior confirmation from certification bodies.
Q: How many distinct temperature conditions are required for full LM-80? A: At least three thermal setpoints including 55°C, 85°C plus one custom application temperature; retest is required if temperature deviation exceeds ±2°C during aging.
Q: Definition of L70? A: L70 stands for the total operating hours when LED luminous flux decays down to 70% of original initial value. For instance L70=54000h means the LED retains ≥70% initial flux after 54,000 working hours.
Disclaimer This article is AI-assisted for reference only and does not constitute certification commitment or legal advice. All implementation shall follow the latest official IES published standards.
