LCD monitor fault reason
When the monitor is used as the monitor terminal of the matrix control system, why does the time synchronization occur when the matrix controller switches the image?
In the monitoring system, the signal of the signal in the output of the image signal of the front end equipment (such as the camera), if there is a phase difference, then the matrix controller to switch between the various images of the signal, the monitor will appear for a period of time synchronization phenomenon, the greater the difference between the different steps. As a result, we should choose the front end device with external synchronization (GEN-LOOK) to construct the monitoring system, and all the front-end devices are used in external synchronization mode, that is, the synchronization of each image signal is controlled by the same synchronous signal, which makes the monitor screen display the same step.
When using the monitor to observe the image, why is it that the image distortion, distortion, distortion, the line field is not synchronized, and even the failure of the input signal.
1, the industry standard of the monitor, the input signal amplitude of professional monitor is 1Vp-P + 3dB (about 1.4Vp-p - 0.7Vp-P), the input impedance is 75 ohm. Therefore, if the input signal due to cable attenuation, impedance mismatch or transmission cable BNC head production is not standardized and other reasons, resulting in the amplitude of the input signal is much lower than 0.7p-p, or because the output of the camera is not standardized or access to some non-standard access devices (such as distributors, amplifiers, etc.), resulting in the signal amplitude is greater than 1.4Vp-p.
2, due to the wide range of video frequency, video signal in the transmission process is more vulnerable to interference (including 50Hz power supply, electromagnetic interference, etc.), thus affecting the image quality. Interference may cause serious distortion, deformation, rolling, row field is not synchronized. Therefore, in the process of monitoring system installation, video line must be far away from the source of electromagnetic interference.
3, front-end equipment, control the potential between the host device and terminal equipment, there is a potential difference can also interfere with the video signal, resulting in image signal distortion or image raceway, if in the charged system access (i.e. front-end equipment, control equipment and terminal equipment are in electrical access BNC connector connecting the front and rear end device through time) may cause surface flashover, the severity of the jump in the fire will destroy the input element or PCB casserole to apply line due to the front end equipment ground (is actually is the shielding layer of cable transmission between potential difference. Open circuit, input no image fault. Therefore, the construction of monitoring system engineering should be strictly according to the design and construction. Earthing busbar shall adopt enough cross-sectional area of copper wire, ensure the fore and aft end surface to surface resistance < 1 ohm, the grounding wire shall form a closed loop, not with strong electricity net zero line short circuit or mixed.