IES LM-79-19 Standard Interpretation: Integrating Sphere, Spectrometer and Goniophotometer Testing Requirements

The IES LM-79-19 standard is an important standard for electrical and photometric testing of LED luminaires, officially released in May 2019 by ANSI (American National Standards Institute) and IES (Illuminating Engineering Society of North America), replacing the LM-79-08 version. The IES LM-79 standard specifies detailed requirements for electrical and photometric testing of LED luminaires, including test environment, test equipment, test methods, and test report requirements. The IES LM-79-19 standard puts forward strict requirements for both integrating sphere testing and goniophotometer testing, requiring the use of high-precision spectrometers and goniophotometers for testing. This article provides a detailed introduction to the various test requirements of the IES LM-79-19 standard, helping readers understand how to test LED luminaires according to the IES LM-79 standard. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system fully comply with IES LM-79-19 standard requirements and can accurately measure the light distribution characteristics and photometric curve data of LED luminaires. Integrating sphere testing and goniophotometer testing are the two main test methods in the IES LM-79 standard. Integrating sphere with spectrometer can measure luminous flux, spectral distribution and other parameters, while goniophotometer can measure light distribution and photometric curves.

I. IES LM-79-19 Standard Overview

The IES LM-79-19 standard is an authoritative standard for electrical and photometric testing of LED luminaires, jointly released by ANSI American National Standards Institute and IES American Illuminating Engineering Society. The IES LM-79 standard replaces the LM-79-08 version and puts forward stricter requirements for test environment, test equipment accuracy, test methods, and test reports of LED luminaires. The IES LM-79-19 standard specifies two main test methods: integrating sphere testing and goniophotometer testing. Integrating sphere testing requires the use of integrating sphere with spectrometer, which can measure luminous flux, spectral distribution, color temperature, color rendering index and other parameters. Goniophotometer testing can measure luminaire light distribution characteristics, photometric curves and luminous intensity distribution. Testing according to the IES LM-79-19 standard can ensure the accuracy and reliability of LED luminaire test results, providing reliable data support for lighting design and luminaire certification. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system fully comply with IES LM-79-19 standard requirements and can accurately measure the light distribution characteristics, photometric curves, and electrical parameters of LED luminaires. Integrating sphere and goniophotometer are indispensable equipment in IES LM-79 standard testing, and spectrometer is the core equipment in integrating sphere testing.

II. Detailed Explanation of IES LM-79-19 Standard Test Requirements

1. Test Environment Requirements (Standard Page 2 Section 2.1, Page 3 Section 4.3, Page 4 Section 4.7)

The IES LM-79-19 standard puts forward strict requirements for the test environment:

• Temperature: 25℃±1.2℃. The test environment temperature must be controlled within the range of 25℃±1.2℃ to ensure the accuracy and repeatability of test results. Temperature control is an important requirement of the IES LM-79-19 standard test environment. Yiming Technology's testing system is equipped with precise temperature control system to ensure the test environment complies with IES LM-79-19 standard requirements.
• Humidity: 10%-65%. The relative humidity of the test environment should be controlled within the range of 10%-65% to avoid the impact of humidity on test results.
• Airflow: 2m/s. The airflow speed in the test environment should be controlled at 2m/s to ensure consistency of luminaire heat dissipation conditions.

These test environment requirements ensure the accuracy and repeatability of LED luminaire test results. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system are equipped with complete environmental control systems and fully comply with IES LM-79-19 standard requirements.

2. Test and Circuit Requirements (Standard Page 4 Section 2.1)

The IES LM-79-19 standard requires luminaire power supply to adopt 4-wire connection:

• 2-wire power supply: Used to provide power to the luminaire
• 2-wire feedback sampling: Used to measure the actual operating voltage and current of the luminaire

The 4-wire connection method can eliminate the impact of line impedance on test results and ensure the accuracy of electrical parameter measurement. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system adopt 4-wire connection method and fully comply with IES LM-79-19 standard requirements, able to accurately measure the electrical parameters of LED luminaires.

3. AC Power Supply Requirements (Standard Page 4 Section 1.2)

The IES LM-79-19 standard puts forward strict accuracy requirements for AC power supply:

• Load regulation: ±0.2%. The load regulation of AC power supply should be controlled within the range of ±0.2% to ensure the stability of power output.
• Accuracy requirements: 1% (reading) + 0.1% (range). The accuracy requirement of AC power supply is 1% (reading) + 0.1% (range).

For example: If the luminaire is powered at 220V with a range of 300V, the actual output voltage should be within 220V±0.26V. This accuracy requirement ensures the accuracy of power output when testing LED luminaires. Yiming Technology's testing system is equipped with high-precision AC power supply and fully complies with IES LM-79-19 standard requirements.

4. DC Power Supply Requirements (Standard Page 4 Section 1.3)

The IES LM-79-19 standard requirements for DC power supply:

• Load regulation: ±0.2%. The load regulation of DC power supply should be controlled within the range of ±0.2%.
• Accuracy requirements: Both voltage and current are 1%. The accuracy of both voltage and current of DC power supply is required to be 1%.

The accuracy requirements of DC power supply ensure the accuracy of LED luminaire DC power supply testing. Yiming Technology's testing system is equipped with high-precision DC power supply and fully complies with IES LM-79-19 standard requirements.

5. Power Meter Requirements (Standard Page 5 Section 3.2)

The IES LM-79-19 standard puts forward detailed requirements for power meters:

• Sampling frequency: 1KHZ-100KHZ. The sampling frequency of power meter should be within the range of 1KHZ-100KHZ.
• Uncertainty requirements:
  • Uncertainty of 5HZ-1KHZ instruments should not exceed 0.6%
  • Uncertainty of 1KHZ-100KHZ instruments should not exceed 2%
  • Note: The uncertainty of instruments is related to the display digits of instruments
• Harmonic testing function: Has harmonic testing function, can test 2-50th harmonics. Power meters should have harmonic testing function and be able to test 2-50th harmonics for analyzing the electrical characteristics of LED luminaires.

The accuracy requirements of power meters ensure the accuracy of LED luminaire power measurement. Yiming Technology's testing system is equipped with high-precision power meters and fully complies with IES LM-79-19 standard requirements, able to accurately measure the power and harmonic characteristics of LED luminaires.

6. Photometric Probe Requirements (Standard Page 9 Section 3.2)

The IES LM-79-19 standard puts forward strict accuracy requirements for photometric probes:

• Cosine response f2 error: Less than 2% (Standard Page 9). The cosine response f2 error of photometric probe should be less than 2% to ensure the measurement accuracy of incident light at different angles.
• f1 error: Less than 3% (Standard Page 9). The f1 error of photometric probe should be less than 3% to ensure the accuracy of spectral response.

The accuracy requirements of photometric probes ensure the accuracy of LED luminaire photometric measurement. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system are equipped with high-precision photometric probes and fully comply with IES LM-79-19 standard requirements, able to accurately measure the luminous flux and light distribution characteristics of LED luminaires.

7. Spectrometer Requirements (Standard Page 9 Section 3.2)

The IES LM-79-19 standard puts forward detailed requirements for spectrometers:

• Wavelength range: 380-780nm. The wavelength range of spectrometer should cover the 380-780nm visible light range.
• Measurement interval: Not less than 5nm. The measurement interval of spectrometer should be not less than 5nm to ensure the completeness of spectral data.
• Wavelength accuracy: 5nm. The wavelength accuracy of spectrometer should be 5nm to ensure the accuracy of wavelength measurement.
• Sensitivity: Reference LM-78-17 (Standard Page 7 Section 2). The sensitivity requirements of spectrometer refer to LM-78-17 standard.

The accuracy requirements of spectrometers ensure the accuracy of LED luminaire spectral measurement. The IES LM-79 standard has very strict requirements for spectrometers, requiring the use of high-precision spectrometers with integrating sphere for testing. Yiming Technology's SPM5000 series integrating sphere spectrometer testing system is equipped with high-precision spectrometers and fully complies with IES LM-79-19 standard requirements, able to accurately measure the spectral distribution, color temperature, color rendering index and other parameters of LED luminaires. Integrating sphere with spectrometer is the standard method for measuring luminous flux and spectral parameters in the IES LM-79 standard.

8. Goniophotometer Requirements (Standard Page 9 Section 3.3)

The IES LM-79-19 standard puts forward detailed requirements for the test interval of goniophotometers. According to different beam angles of luminaires, the test interval requirements are also different:

• Luminaire beam angle not greater than 20°:
  • 100%-50% use test interval not greater than 1°
  • 50%-10% use test interval not greater than 2°
  • 10%-0% use test interval not greater than 5°
• Luminaire beam angle greater than 20°:
  • 100%-50% use test interval not greater than 2°
  • 50%-0% use test interval not greater than 5°

The test interval requirements of goniophotometers ensure the accuracy of LED luminaire light distribution measurement and the completeness of photometric curve data. The IES LM-79 standard has very strict requirements for goniophotometer test intervals, requiring appropriate test intervals to be selected according to luminaire beam angles. Yiming Technology's GMS goniophotometer testing system fully complies with IES LM-79-19 standard requirements and can automatically adjust test intervals according to luminaire beam angles, accurately measuring the light distribution characteristics and photometric curve data of LED luminaires. Goniophotometer is the standard equipment for measuring light distribution and photometric curves in the IES LM-79 standard, complementing integrating sphere testing methods to complete comprehensive LED luminaire testing.

9. Warm-up Stability Requirements (Standard Page 7 Section 4)

The IES LM-79-19 standard puts forward strict requirements for warm-up stability:

• Monitoring time: Monitor for at least 30 minutes. LED luminaires need to warm up for at least 30 minutes to ensure reaching stable state.
• Reading requirements: Obtain at least 3 photometric and electrical power readings within 20 minutes. Obtain at least 3 photometric and electrical power readings within 20 minutes.
• Stability judgment: If the difference between the maximum and minimum values in the readings divided by the current point value is less than 5%, it is considered to have reached steady state. If the difference between the maximum and minimum values in the readings divided by the current point value is less than 5%, it is considered to have reached steady state.

Warm-up stability requirements ensure that LED luminaires are in stable state during testing, and test results are accurate and reliable. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system are equipped with automatic warm-up monitoring functions and fully comply with IES LM-79-19 standard requirements, ensuring the accuracy of test results.

10. Test Report Requirements (Standard Page 12 Section 1)

The IES LM-79-19 standard puts forward detailed requirements for test reports. Test reports should include the following content:

• Test time and test laboratory: Record the specific test time and the name of the laboratory conducting the test
• Luminaire manufacturer name: Record the name of the luminaire manufacturer
• Optical parameter testing: Test results of optical parameters such as luminous flux, radiant flux, photon flux, etc.
• Electrical parameter testing: Test results of electrical parameters such as AC/DC voltage, current, power factor, power, etc.
• Calculated values: Calculated values such as luminous efficacy, color uniformity, etc.
• Ambient temperature: Ambient temperature during testing
• Equipment measurement conditions: Measurement conditions of goniophotometer variable angle photometry or integrating sphere spectroscopy. The IES LM-79 standard requires clear indication of whether integrating sphere testing or goniophotometer testing is used.
• For integrating sphere testing: Integrating sphere coating reflectance, integrating sphere diameter, 4π or 2π testing method. The IES LM-79 standard requires that integrating sphere test reports must include detailed parameters of the integrating sphere, including integrating sphere coating reflectance, integrating sphere diameter and testing method (4π or 2π). Integrating sphere with spectrometer can measure luminous flux, spectral distribution and other parameters.
• For goniophotometer testing: Parameters such as measurement distance. The IES LM-79 standard requires that goniophotometer test reports must include key parameters such as measurement distance. Goniophotometer can measure luminaire light distribution and photometric curves.
• SI traceability: SI traceability information of test equipment
• Self-absorption correction coefficient: Self-absorption correction coefficient during integrating sphere testing
• Luminous intensity: Luminous intensity distribution data of luminaires
• Chromaticity coordinates, color temperature, color rendering index: Color parameters of luminaires
• Color fidelity and color saturation index: ANSI/IES TM-30-18 standard parameters (Rg, Rf, Local Chroma Shift, Local Hue Shift)
• Spectral distribution: Spectral power distribution data of luminaires

Test report requirements ensure the completeness and traceability of test results. The IES LM-79 standard requires that test reports must clearly indicate the test method used (integrating sphere testing or goniophotometer testing) and corresponding equipment parameters. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system can automatically generate complete test reports that comply with IES LM-79-19 standard requirements, including all necessary test data and parameters. Whether using integrating sphere with spectrometer for testing or using goniophotometer for testing, complete test reports must be generated according to IES LM-79 standard requirements.

Summary

The IES LM-79-19 standard is an important standard for electrical and photometric testing of LED luminaires, jointly released by ANSI American National Standards Institute and IES American Illuminating Engineering Society, replacing the LM-79-08 version. The IES LM-79 standard puts forward stricter requirements for test environment, test equipment accuracy, test methods, and test reports, including test environment (temperature 25℃±1.2℃, humidity 10%-65%, airflow 2m/s), test and circuit requirements (4-wire connection), AC power supply accuracy (load regulation ±0.2%, accuracy 1% (reading) + 0.1% (range)), DC power supply accuracy (load regulation ±0.2%, accuracy 1%), power meter requirements (sampling frequency 1KHZ-100KHZ, uncertainty requirements, harmonic testing function), photometric probe accuracy (cosine response f2 error less than 2%, f1 error less than 3%), spectrometer requirements (wavelength range 380-780nm, measurement interval not less than 5nm, wavelength accuracy 5nm), goniophotometer test interval requirements (different intervals according to beam angles), warm-up stability requirements (monitor for at least 30 minutes, stability judgment), and detailed test report requirements. The IES LM-79 standard specifies two main test methods: integrating sphere testing and goniophotometer testing. Integrating sphere testing requires the use of integrating sphere with spectrometer, which can measure luminous flux, spectral distribution, color temperature, color rendering index and other parameters. Goniophotometer testing can measure luminaire light distribution characteristics, photometric curves and luminous intensity distribution. The IES LM-79 standard puts forward strict accuracy requirements for integrating sphere, spectrometer and goniophotometer.

Testing LED luminaires according to the IES LM-79-19 standard can ensure the accuracy and reliability of test results, providing reliable data support for lighting design and luminaire certification. The IES LM-79 standard has very strict requirements for test equipment, requiring high-precision test equipment and environmental control systems. The IES LM-79 standard requires the use of high-precision integrating sphere with spectrometer for luminous flux and spectral testing, and high-precision goniophotometer for light distribution and photometric curve testing. Yiming Technology's GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system fully comply with IES LM-79-19 standard requirements and can accurately measure all parameters of LED luminaires including light distribution characteristics, photometric curves, electrical parameters, spectral distribution, color temperature, color rendering index, etc., automatically generating complete test reports that comply with IES LM-79-19 standard requirements. Integrating sphere, spectrometer and goniophotometer are core equipment in IES LM-79 standard testing and must be configured and used strictly according to IES LM-79 standard requirements.

As a professional LED lighting testing equipment manufacturer, Yiming Technology deeply understands the importance of the IES LM-79-19 standard and has developed GMS goniophotometer testing system and SPM5000 series integrating sphere spectrometer testing system that fully comply with IES LM-79-19 standard requirements. The IES LM-79 standard puts forward strict accuracy requirements for integrating sphere, spectrometer and goniophotometer. Yiming Technology's testing systems are equipped with high-precision integrating sphere, high-precision spectrometer and high-precision goniophotometer, fully meeting IES LM-79 standard requirements. Yiming Technology's testing systems are equipped with high-precision test equipment, complete environmental control systems, and automatic testing software, able to accurately measure all parameters of LED luminaires according to IES LM-79-19 standard and generate complete test reports that comply with IES LM-79-19 standard requirements. Whether using integrating sphere with spectrometer for testing or using goniophotometer for testing, Yiming Technology's testing systems can complete testing strictly according to IES LM-79 standard requirements. Yiming Technology is committed to providing professional IES LM-79-19 standard testing services and test equipment for customers, including high-precision integrating sphere, spectrometer and goniophotometer, helping customers accurately evaluate the performance of LED luminaires, jointly promoting the standardized development of the lighting industry.