LED display in the eyes of the staff of the Entry-Exit Inspection and Quarantine Bureau

Some time ago, I had pushed the staff of the Entry-Exit Inspection and Quarantine Bureau to talk about the LED lighting inspection. Let's take a look at the requirements of the LED display in the eyes of the staff of the Entry-Exit Inspection and Quarantine Bureau.

China's LED display technology has gradually matured, but due to a variety of factors, there are still many problems in the quality of newly installed display. Some display lights are off, mosaic is serious; some screen images are blurred and rough; some displays require endless repair and maintenance.

One of the main reasons for these undesirable phenomena is that the quality of LED display is not in place. At present, the quality of LED display in China needs to be further improved. Based on my experience in the entry-exit inspection and quarantine bureau, this paper briefly introduces the quality standards of China's LED display industry. On this basis, a brief analysis of the factors affecting the quality of LED display screens is hoped to promote LED for China. The quality of the display is improved.

LED display industry quality standards


The "General Specification" is the main technical basis for display technology in China. It is perfectly suited for text, graphics, video and other graphic displays indoors and outdoors in LEDs. Its content consists of eight parts: scope, normative references, terms and definitions, classifications, requirements, inspection methods, inspection rules, packaging, transportation, storage, etc.

The "Requirements" section proposes 10 main requirements including: LED display hardware environment, LED display software environment, structure and appearance, security requirements, LED display function, LED display electrical characteristics, LED display power supply, environmental adaptability and reliability Sex.

LED display quality requirements


(1) Brightness requirements

Brightness is an important indicator of the quality of the display. The brightness of the display is mainly determined by the luminous intensity of the LED and the density of the display. Some LED displays are mounted on very high exterior walls, and the mounting angle of the LED screens also affects the lighting intensity of the human eye. The brightness of the LED display defines the intensity of light per unit area of ​​the screen in the SJ/T11141-2003.LLD display general specification.

The color of the LED screen display is monochrome, two-color and full-color. It can be divided into indoor and outdoor by using the environment, and the parameters of the LED display are different for different colors and environments. The indoor full-color LED display requires a brightness of 800 cd/m2, while the outdoor full-color LED display requires 1500 cd/m2 for such brightness to basically guarantee the screen image display policy. In recent years, the various technologies of LED display have been further developed, and the use of materials and propagation processes are more mature. As a result, the luminous efficiency requirements of LED displays produced by manufacturers are greatly improved.

(2) Chroma requirements

The LED display has the characteristics of color reproduction. Some manufacturers are not aware of the advantages of the wide color gamut of LED displays, blindly pursuing the high brightness of the screen, which leads to the color distortion of the produced LED display, the display of glare, and sometimes the information playback will make the audience uncomfortable.

Therefore, when the LED display is produced, it is necessary to evaluate its color index. If the color index can meet the corresponding requirements, the color matching is appropriate and will not cause discomfort. The temperature measurement of the color temperature and chromaticity coordinates of the center position of the full-color LED display needs to be less than 6500K, so that the color of the full-color LED display can be prevented from being too cold, and the relevant color temperature is not more than the specified range.

(3) Energy efficiency requirements

Different LED displays want to achieve the same display, and the power consumption of the screen may be different. In today's promotion of energy saving, emission reduction and environmental protection, the energy efficiency requirements of LED displays are also very important.

Energy efficiency evaluation LED products generally use luminous efficiency. The installation and use range of the LED display, the measurement of the illuminance of the LED display is extremely difficult, and the brightness is relatively easy. By studying the definition of brightness and luminous flux, the energy efficiency of the LED display is found, and the luminance of the LED display is multiplied by the hemispherical surface, and the calculation result is the luminous flux.

LED display screens are mostly large screens, and there may be some uneven brightness. In order to evaluate the energy efficiency of the LED display in a more objective and reasonable way, the LED is displayed in a bright state, and it is necessary to randomly select 9 different points in all directions, and the brightness of 9 points is simultaneously measured, and then the LED display is obtained. The average brightness of the screen, expressed in LAV. When measuring the brightness, measure the power consumption of the LED display, and according to the formula, the energy efficiency (in lm/W) of the LED display can be obtained.

η=πSLAV / P
Where: π represents the solid angle (sr);
S represents the light-emitting area of ​​the display screen (m2);
LAV indicates the average brightness of the display (cd/m2);
P is the maximum power consumption (W) of the display.

(4) Environmental protection and safety requirements

Because the use of the display is often in different situations, different environments have different security requirements for the LED display. The main safety standards include: grounding, leakage current, temperature rise and medium strength. The most important of these four items is the leakage current and insulation strength requirements. SJ /11141- 2003T display general specification requires standard 1.1 times rated power supply voltage, leakage current should not exceed 3.5mA, the power switch connected to the power switch should be tolerant 1500 v, 1 minute test will not insulation breakdown.

The number of outdoor LED displays is much higher than indoors. The indoor display environment has lower requirements for adaptability, while the outdoor display is much higher than the environmental adaptability requirements. Due to the different environments and different environments, the outdoor display should be able to withstand the long-term effects of harsher environments, such as wind, rain, earthquakes, and normal use in high temperature and low temperature environments.

Conclusion


In China, the LED display screen is widely used with the advertisements of major media and the information notification of the traffic management department, and has a large audience. Therefore, it is necessary to ensure the quality of the LED display screen. Manufacturers must pay attention to the LED display brightness requirements, color requirements, energy efficiency requirements and environmental protection and safety requirements to meet the requirements of use and extend the life cycle of the product.

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