Analysis of signal interference shielding technology in liquid crystal splicing screen system
With the progress and development of the society, the transmission and conversion of information are highly integrated with our life. As one of the terminal display devices for information, the LCD splicing screen is shining brightly and has been applied by many industries, now we can often see the footprint of the LCD splicing screen in our daily work.
Now let's make a systematic analysis and investigation of the common signal interference of LCD splicing screen: 1. There is a strong interference source near the system. This can be judged through investigation and understanding.
If this is the case, the solution is to strengthen the shielding of the camera, and to ground the pipeline of the video cable, etc. 2. The quality of the video transmission line is not good, especially the shielding performance is poor (
The shielded mesh is not a good quality copper wire mesh, or the shielded mesh is too thin to be shielded).
At the same time, the line resistance of this kind of video line is too large, thus causing large signal attenuation, which is also the cause of aggravating the fault.
In addition, the characteristic impedance of this kind of video cable is not 75Ω and the parameter exceeds the regulations, which is also one of the causes of the failure. 3. The failure caused by the short circuit and open circuit between the core wire of the video cable and the shielding network.
The manifestation of this kind of fault is to generate deep and chaotic large-area reticulate interference on the monitor, so that all images are destroyed and no images and synchronous signals are formed.
This situation often occurs on BNC connectors or other types of video connectors.
That is, when this kind of fault phenomenon occurs, the liquid crystal splicing Wall often does not cause problems in all signals of the whole system, but only in those roads with bad joints.
As long as these connectors are carefully checked one by one, 4, caused by the power supply of the power supply system can be solved. Interference signals are superimposed on the normal power supply.
However, the interference signals on this kind of power supply mostly come from the equipment using SCR in this power grid.
In particular, high-current and high-voltage silicon controlled devices pollute the power grid very seriously, which leads to unclean' power supplies in the same power grid '.
For example, there are high-power SCR frequency modulation speed regulating devices, SCR rectification devices, scr ac/DC conversion devices, etc. in this power grid, which will pollute the power supply.
The solution to this situation is relatively simple. As long as the whole system of the liquid crystal splicing screen is powered by a purified power supply or an on-line UPS, the space radiation interference introduced by the transmission line can be basically solved.
This kind of interference phenomenon is mostly caused by strong and high frequency space radiation sources near the transmission system, system front end or central control room.
One of the solutions to this situation is to have an understanding of the surrounding environment when the system is established and try to avoid or stay away from radiation sources as far as possible;
Another method is to strengthen the shielding of the front end and the central equipment when the radiation source cannot be avoided, and to use steel pipes for the pipelines of the transmission line and to be well grounded. 6. Fault phenomena caused by mismatched characteristic impedance of the transmission line.
The manifestation of this phenomenon is that several vertical bars with equal spacing are generated on the monitor screen, and the frequency of the interference signal is basically an integer multiple of the line frequency.
It can also be said that this kind of interference phenomenon is caused by the combination of the characteristic impedance and distribution parameters of the video cable of the liquid crystal splicing wall system that do not meet the requirements.
The solution is generally solved by the method of 'starting end in series with resistance' or 'terminal in parallel with resistance.