In the security monitoring system, displaying the images sent from the front of the system through the monitor is an indispensable display terminal of the monitoring system, and is the most important part of the monitoring system in addition to the camera. With the increasing demand for security, people’s public safety has also received more and more attention. In particular, security video surveillance systems, as an effective means of security protection, are increasingly receiving widespread attention from all walks of life.
Common fault analysis
When a monitor is used as a monitor terminal of a matrix control system, why does the synchronization occur for a period of time when the matrix controller switches images?
In the monitoring system, if there is a phase difference between the field sync signals in the image signals output from each front-end device (such as a camera), the monitor will display a period of non-synchronization when the matrix controller switches the image signals of each channel. The larger the phase difference, the longer the time that is not synchronized. Therefore, it is recommended that when constructing a monitoring system, front-end devices with GEN-LOOK input should be used as much as possible, and all front-end devices should use external synchronization. That is, the synchronization of each image signal is controlled by the same synchronization signal. Causes the monitor screen to show sync.
When using the monitor to observe the image, why does the image distortion, distortion, line and field synchronization, or even failure of the input signal occur?
1. The monitor's industry standard specifies that the input amplitude of the professional monitor is 1Vp-P±3dB (about 0.7Vp-P-1.4Vp-p), and the input impedance is 75 ohms. Therefore, if the input signal is not standardized due to cable attenuation, impedance mismatch, or the BNC head of the transmission cable, the input signal amplitude is much lower than 0.7 pp; either the camera output is not regulated or some irregularity is connected. When the input signal (such as distributor, amplifier, etc.) causes the input signal amplitude to be much larger than 1.4Vp-p, it may cause image distortion, line and field synchronization, etc.
2. Due to the wide video frequency range, video signals are more susceptible to interference during transmission (including 50Hz power interference, electromagnetic interference, etc.), which affects the image quality. Severe disturbances may cause images to be distorted, deformed, raceways, and lines and fields to be out of sync. Therefore, during the installation of the monitoring system, the video line must be far away from sources of electromagnetic interference.
3. The potential difference between the front-end device, the control host device and the terminal device may also interfere with the video signal, resulting in distortion of the image signal or image appearance of a race track, if the whole system is powered on (ie, the front-end device, the master When the equipment and terminal equipment are connected to the BNC head to connect the front and rear equipment when they are powered on, it may be caused by the potential difference between the ground wire of the front and rear equipment (actually the shielding layer of the transmission cable). Fire, this severe flash fire will destroy the components at the input or the ground line in the PCB board casserole. Causes the input to open circuit and input no image fault. Therefore, the construction of monitoring system engineering should be designed and constructed in strict accordance with the specifications. The grounding bus should use copper conductors with sufficient cross-sectional area to ensure that the ground-to-ground resistance of the front and rear ends is <1Ω. The grounding line must not form a closed loop, and must not be short-circuited or mixed with the strong grid neutral line.
Common fault analysis
When a monitor is used as a monitor terminal of a matrix control system, why does the synchronization occur for a period of time when the matrix controller switches images?
In the monitoring system, if there is a phase difference between the field sync signals in the image signals output from each front-end device (such as a camera), the monitor will display a period of non-synchronization when the matrix controller switches the image signals of each channel. The larger the phase difference, the longer the time that is not synchronized. Therefore, it is recommended that when constructing a monitoring system, front-end devices with GEN-LOOK input should be used as much as possible, and all front-end devices should use external synchronization. That is, the synchronization of each image signal is controlled by the same synchronization signal. Causes the monitor screen to show sync.
When using the monitor to observe the image, why does the image distortion, distortion, line and field synchronization, or even failure of the input signal occur?
1. The monitor's industry standard specifies that the input amplitude of the professional monitor is 1Vp-P±3dB (about 0.7Vp-P-1.4Vp-p), and the input impedance is 75 ohms. Therefore, if the input signal is not standardized due to cable attenuation, impedance mismatch, or the BNC head of the transmission cable, the input signal amplitude is much lower than 0.7 pp; either the camera output is not regulated or some irregularity is connected. When the input signal (such as distributor, amplifier, etc.) causes the input signal amplitude to be much larger than 1.4Vp-p, it may cause image distortion, line and field synchronization, etc.
2. Due to the wide video frequency range, video signals are more susceptible to interference during transmission (including 50Hz power interference, electromagnetic interference, etc.), which affects the image quality. Severe disturbances may cause images to be distorted, deformed, raceways, and lines and fields to be out of sync. Therefore, during the installation of the monitoring system, the video line must be far away from sources of electromagnetic interference.
3. The potential difference between the front-end device, the control host device and the terminal device may also interfere with the video signal, resulting in distortion of the image signal or image appearance of a race track, if the whole system is powered on (ie, the front-end device, the master When the equipment and terminal equipment are connected to the BNC head to connect the front and rear equipment when they are powered on, it may be caused by the potential difference between the ground wire of the front and rear equipment (actually the shielding layer of the transmission cable). Fire, this severe flash fire will destroy the components at the input or the ground line in the PCB board casserole. Causes the input to open circuit and input no image fault. Therefore, the construction of monitoring system engineering should be designed and constructed in strict accordance with the specifications. The grounding bus should use copper conductors with sufficient cross-sectional area to ensure that the ground-to-ground resistance of the front and rear ends is <1Ω. The grounding line must not form a closed loop, and must not be short-circuited or mixed with the strong grid neutral line.
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