According to IESNA-LM-79, How to Choose the Integrating Sphere and Goniophotometer

IESNA-LM-79 (Electrical and Photometric Measurements of Solid-State Lighting Products) is a standard made by Illuminating Engineering Society of North America; this standard put forward the measurement standard and method, which clarify the test parameters, testing equipments, measurement rules and etc. The key point for this standard is to provide guidance for testing the luminous flux, color temperature, color rending index, power, light intensity distribution, color repeatability, IES file and etc. LM-79 recommends two systems to finish the testing, that is goniophotometer and integrating sphere with spectroradiometer system.

According to LM-79, there are two methods to test the total luminous flux: one is integrated spectrophotometry; for this way, it recommends the integrating sphere with spectroradiometer to do the luminous flux testing, like LPCE-2 (LMS-9000) made by Lisun. The other is variable angle spectrophotometry; for this way, it recommends the mirror rotation goniophotometer to do the luminous flux testing, like LSG-2000 made by Lisun. But either goniophotometer or intergrating sphere, they have their own advantage and disadvantage. Integrating sphere system is an economic way, user can choose difference size of sphere depends on the lamp, and the test result is acceptable by most companies. But the disadvantage is when you test the big lamp, like HID lamp, the self-absorption is a big problem, because when the lamp is lit up, the interior of the sphere will unavoidable absorb a part of light, then affect the accuracy. Although, auxiliary lamp is commonly applied to remedy the light which is absorbed by integrating sphere, anyhow, the precise will decrease. So, in order to solve this problem, the standard makers like IEC, CIE, IESNA-LM-79 recommend the mirror rotation goniophotometer to test luminous flux of the big lamp, in this way, the test result will more accuracy. At the moment, most third-labs and state institutes choose the mirror rotation goniophotometer; surely, for the productive enterprises, they choose luminaire rotation goniophotometer (like LSG-1800CCD and LSG-1800B made by Lisun) because of the high cost performance, and especially it can meet the demands for luminous intensity distribution and IES file testing.

When choose integrating sphere or goniophtometer to test the lamp, it is no only depends on the lamp size, but also the other parameters requested. For example, besides the luminous flux, the CCT, CRI, chromaticity coordinates, wavelength and other color parameters are requested, then integrating sphere with spectroradiometer is recommended. If the user request the IES file, luminous intensity distribution and etc, then the goniophotometer is recommended.

According to LM-79, Clause 9.3.1, Lisun developed the LSG-2000 mirror rotation goniophotometer. The working principle of LSG-2000 keeps the position of lighting fixture no move and rotation the reflect mirror, to make sure the high accuracy. Because there are several factors will affect the accuracy in the certain environment: resolution, range of view angle, vibration, air flow, temperature and etc. But the key factors are vibration, air flow and temperature. But for double pillars or single pillar luminaire rotation goniophotometer, rotate the lamp will cause the air flow and temperature changing, so that to affect the accuracy. And the vibration will also affect the accuracy, but along with the technical developing, the advanced power device and control technology will greatly decrease the vibration. LSG-2000 is adopted to test luminous intensity, luminous intensity distribution, area luminous flux, light efficiency, utilization factor, glare, brightness limit curve, isocandela curve, isolux curve and etc.

According to LM-79 Clause 9.1, Lisun developed LPCE-2(LMS-9000) high accuracy spectroradiometer and integrating sphere system. The difference between LSG-2000 and LPCE-2 (LMS-9000A) is the tested parameters. LPCE-2(LMS-9000A) is applied to test the photometric, colorimetric and electric parameters of LED, like luminous flux, CCT, CRI, chromaticity coordinates, light efficiency, voltage, current and etc. Meanwhile, the test software of LPCE-2(LMS-9000A) also combined the LED maintenance testing function to meet the requirements of LM-80. It can record the LED optical attenuation curve (luminous flux VS time), but the price is reasonable.

In the integrating sphere system, it is very important to choose the right size of integrating sphere. According to LM-79 Clause 9.1.1, dia. 1m or larger sphere is suitable for compact lamp, like incandescent lamp, compact fluorescent lamp; dia. 1.5m and larger sphere is suitable for larger lamp, like 4ft linear fluorescent lamp, HID lamp and etc. Dia. 2m and larger sphere is suitable for certain lamp, like 500W or larger lamp. Besides the sphere size, the test geometry is also important when choose the right sphere, there are two kinds of geometry, that is 4πgeometry and 2πgeometry. 2πis only applied to emitting light forward direction and some lamps with big shell, but 4πis applied to emitting light in all direction.

LSG-2000 mirror rotation goniophotometer and LPCE-2(LMS-9000A) integrating sphere system are widely used in some third-labs and big companies, like Sharp Electronics in Memphis TN in America, CS Tech Mexico S.A. de C.V in Mexico, SGS Australia, World Testing Lab in Italy, Institute of Testing and Certification India Pvt. Ltd in India. The reason why Lisun Electronics can win so many orders from these famous Third-labs and companies is because Lisun always following and practicing the motto of Right products, Right price and Right service. See from the feedback, Lisun’s products and service enjoys good reputation in the world market. No matter in the pass or future, Lisun will always bring the good quality and superior service for all the users, and welcome you to send an inquiry to us.