In the monitoring system, if there is a phase difference in the field synchronization signal of the image signal output by each front-end device, the LCD monitor will experience a period of asynchronous phenomenon when the matrix controller switches between various image signals. The larger the phase difference, the longer the asynchronous time. Therefore, it is recommended to choose front-end devices with external synchronization input as much as possible when building monitoring systems, and all front-end devices should use external synchronization mode, that is, the synchronization of each image signal is controlled by the same synchronization signal, which promotes the synchronization of the LCD monitor screen display.

in useLCDWhy do we sometimes encounter faults and phenomena such as image distortion, distortion, unsynchronized line field, or even no input signal when observing images?

1LCDAccording to industry standards, the input signal amplitude for professional LCD monitors is 1Vp-P ± 3dB, and the input impedance is 75 ohms. Therefore, if the input signal amplitude is much lower than 0.7p-p due to cable attenuation, impedance mismatch, or non-standard BNC head manufacturing of the transmission cable, etc; Or when the input signal amplitude is much greater than 1.4Vp-p due to non-standard camera output or the connection of some non-standard access devices, it may cause image distortion, line field asynchrony, and other phenomena.

2. The potential difference between front-end devices, control host devices, and terminal devices can also interfere with video signals. According to the introduction of Youse Display, it can cause distortion of image signals or rolling of images. If the entire system is connected with power, ground to ground flashover may occur due to the potential difference between the ground wires of the front-end and back-end devices. In severe cases, this flashover can damage the components at the input end or the ground level wiring in the PCB sand pot. Causing an open circuit at the input end and no image fault at the input. Therefore, the construction of monitoring system engineering should strictly follow the specifications for design and construction. The grounding busbar should use copper wires with sufficient cross-sectional area to ensure that the ground to ground resistance at the front and rear ends is less than 1 Ω. The grounding wire should not form a closed loop and should not be short circuited or mixed with the neutral wire of the strong power grid.

3. Due to the wide frequency range of videos, video signals are more susceptible to interference during transmission, which can affect image quality. Severe interference may cause image distortion, deformation, rolling paths, and unsynchronized fields. Therefore, during the installation of the monitoring system, the video cable must be kept away from electromagnetic interference sources.