LED test: errors frequently happened

Usually, in LED test, luminous flux, CRI, color temperature and power deviation are four major aspects that with relatively high failure rates. Unqualified quality testing results mainly concentrate in four aspects: 1. Electrical insulation cannot meet the corresponding requirements: insufficient internal clearance and creepage distance, with touchable conductors (not safely isolated). Especially for some small sized LED lamps, the compact structure forced manufacturers to ignore the requirements of electrical insulation. 2. Using drivers that cannot meet the safety requirements of LED power supplies, or using simple buck circuit to drive LED lamps. 3. Electromagnetic disturbance voltage exceeds standards: most of LED drivers use cheap but weak circuits without any anti-electromagnetic measures, leading to conduction voltage and radiation exceeding. 4. Cannot meet the light and color performance requirements. LED light-emitting principles have huge differences with traditional lighting technologies. Many designers only concerned about whether their products can send out light normally, but ignore the quality of photometric and colorimetric requirements, resulting in the huge differences in color temperature deviation and low CRI.

 

Usually, in LED test, luminous flux, CRI, color temperature and power deviation are four major aspects that with relatively high failure rates.

 

In LED test, lamps from one manufacturer may get different testing results in different testing processes. There are three main reasons that cause to such situation:

 

1)       Testing system errors. This error is within the allowable range. Due to production process deviations, it is very hard for different testing system to stay exactly the same. There must be some errors. Traditional light fitting with error less than 1.5% are qualified. However, tests for LED lighting products have not been standardized. The permissible error range of LED lighting products is relatively vague, generally between 3% and 5%.

 

2)       Error comes from different testing environment. Lamps’ working environment along with the different surface contamination will exert huge influence on testing results, 7%-8% error. Especially for some products which used light-emitting surfaces as the secondary optical lens. These products have concave and convex structures. Dust and dirt can easily accumulate on the surface, hardly to clean up, which seriously affect the luminous flux and furthermore the light distribution.

 

3)       Errors come from equipment deviations and standard errors. Normal LED test includes: spherical integral devices, devices for light distribution measurement and equipments for light radiation. Spherical integral devices are used to measure the luminous flux of LED lights.