How to distinguish the quality of LED display?

I.LED wavelength control range 

The wavelength determines whether the color is pure and whether the color is consistent. The way to tell the difference is simple; Users generally do not have professional equipment, how can they be distinguished by their eyes? First: the whole screen is white, and the screen should be pure white, without any other noise. Second: play red, green, blue monochrome, the color of the center wavelength is what we usually call positive blue, positive red and green, if the color is darker or lighter, it proves to be a partial wavelength. If a certain color is inconsistent, it proves that the wavelight difference is too large, and the high-quality display screen is in the range of the center wavelength, the blue-green wavelength difference is controlled at 3nm, and the red wavelength difference is less than 5nm.

II. The angle of view of the light-emitting tube 

The luminous angle of the light-emitting tube refers to the angle between the two observation directions and the normal direction of the same plane when the brightness of the observation direction drops to one-half of the brightness of the normal direction of the LED display. It is divided into horizontal and vertical viewing angles. 

For outdoor LED displays, elliptical light-emitting tubes or SMD light-emitting tubes are generally used, elliptical light-emitting tubes have the characteristics of small angles and high brightness, and the vertical angle of view of SMD light-emitting tubes is much larger than that of elliptical tubes, but its brightness is smaller than that of elliptical light-emitting tubes. For indoor LED displays, due to their low brightness requirements and wide audience area, SMD light-emitting tubes are the best choice. It should be noted that in order to reduce costs and confuse users, some manufacturers of light-emitting tubes in the market have made the brightness of the light-emitting tube relatively high, and the angle of view is smaller than that of the conventional light-emitting tube, which will lead to the LED display the brightness is very high on the front, but the image can not be seen clearly when viewed at a relatively large angle on the side. 

In order to improve the brightness, small size LED chips are usually packaged with small angles. Larger sizes don't need to be packaged at a small angle because they don't need that much brightness. Therefore, a large angle (110) with high brightness and low current is the best. 

III. Maximum brightness 

The maximum brightness refers to the brightness of each primary color of the LED display at the highest gray level and the highest brightness under a certain ambient illumination. In a nutshell, it is the brightness measured in the normal direction using a light gun when the display is set to white 255 levels using software. 

For outdoor LED displays, according to the use of the environment, there will be different requirements for the maximum brightness, because in the context of strong ambient light, the brightness of the LED display is required to be higher, so that the masses can see the content displayed on the screen clearly.

IV.Square power consumption 

The power consumption of LED display generally has two indicators, one is the maximum power consumption, and the other is the use of power consumption. The maximum power consumption refers to the power consumption of the LED display at the maximum brightness, how to distinguish the maximum power consumption with the eye? The method is very simple: look at the number of power supplies behind the box, multiply by the maximum power of each power supply, and calculate the maximum power consumption per square meter according to the size of the box, and there are two kinds of power supplies generally used, 200W and 300W power supply. The use of power consumption refers to the usual play of advertising video, text, pictures when the power consumption, because the use of power consumption and the content played has a direct relationship, so it is difficult to have an exact value, but according to our experience, generally 1/3 of the maximum power consumption. Lower power consumption means lower cost of use and less heat, and the amount of heat depends on the current and directly affects the service life and stability of the display. 

Energy-saving LED displays use four 200w power supplies per square meter, so the maximum power consumption will not exceed 680w per square meter. Because the effective output of the power supply is basically at 85%.

V. Refresh rate 

Refers to the number of times that the LED display information is fully displayed per second, in Hz. If the refresh rate is too low, the LED display will shake when the human eye looks at it, and a scan line will appear when shooting through the camera. The general human eye requires the refresh rate to be more than 300Hz, that is, as long as the refresh rate exceeds 300Hz, the average person will not have a feeling of shaking when watching the LED display with the naked eye, and if you use the camera to shoot, according to the different settings of different cameras, it is generally required at least 600Hz or more to capture the scan line. A high refresh can improve the brightness and color fidelity of the display. It can be detected with a digital camera, and if it is a high refresh, the picture taken by the camera is very clear, and there are no snowflakes and scan lines. This indicator is particularly important when renting screens and televising.

VI. Contrast 

Contrast refers to the measurement of different levels of brightness between the brightest white and the darkest black in the light and dark areas of an image, with a larger range representing greater contrast and a smaller range representing smaller contrast. The impact of contrast on visual effects is very critical, generally speaking, the greater the contrast, the clearer and more eye-catching the image, and the more vivid and vivid the colors; And if the contrast is small, the whole picture will be gray. In order to improve the contrast of LED display, the use of all-black LED is currently the most effective method.

VII. Circuit design part 

The design and materials of the circuit board play a vital role in the stability and display effect of the LED display. There are mainly the following requirements:

1. Requirements for materials: PCB thickness, generally 1.6mm thickness; Material: FR-4 fiberglass board, some manufacturers may use FR-2 paper substrate in order to reduce costs; Copper foil thickness: The thickness of copper foil has a non-negligible role in the heat dissipation of PCB board and the stability of the circuit, the normal copper foil thickness is 35um (1Oz), and some manufacturers will use 18um (0.5Oz) copper foil thickness to shoddy; So how do you discern as a consumer? You can take an empty PCB and distinguish it by weight, under normal circumstances, the heavier, the better. 

2. Several key points in design: connector, connector refers to the connector between the module and the module, there are two main ones that are used more on the market now, one is the horn, the other is the pin header, the advantage of the horn is that the cable can be stuck through the two card positions, and it is not easy to cause failure caused by the connector problem; The choice of electrolytic capacitors and tantalum capacitors, tantalum capacitors are undoubtedly the first choice for occasions that require long life, and electrolytic capacitors are the first choice for occasions that require low prices.

VIII. Automated production equipment 　

Most of the LED display is electronic components, and static electricity has a very big harm to electronic components, sometimes static electricity directly breaks down the components to make it damaged, sometimes it does not break down directly, but it leaves hidden dangers, and the side effect is that the components are damaged after a period of time. In the electronics manufacturing industry, people think of many ways to deal with artificial static electricity, including wearing electrostatic rings, wearing electrostatic clothing, using dust-free workshops and so on. In fact, the most effective way is to minimize human contact with electronic components, and the use of automation equipment achieves this goal.