Video surveillance system several major issues

Video surveillance is an important part of the security system, including front-end cameras, transmission cables, and video surveillance platforms. The cameras can be divided into network digital cameras and analog cameras, which can be used as front-end video image signal acquisition. It is a comprehensive system with strong prevention capabilities. With the development, more and more public places use video surveillance systems, and the quality of products is uneven. The consequent system failures frequently occur.

1. Incorrect power supply caused by equipment failure Solution: Incorrect power supply can be roughly as follows: power supply line or power supply voltage is not correct, power is not enough (or the path of a road power supply line is not enough, buck is too large, etc.) Short circuit, open circuit, instantaneous overvoltage, etc. occur in the transmission lines of the power supply system. In particular, the device may be damaged due to power supply errors or instantaneous overvoltage.

2. As some lines, especially those connected to the equipment, are not handled well, circuit breakers, short-circuits, poor insulation between the lines, miswiring, etc. result in damage to the equipment (or components), performance degradation, or failure of the equipment itself. , but the phenomenon is reflected in the equipment or components. In particular, the quality of some connectors is poor, and the connection process is not good. This is a common cause of problems.

Solution: In this case, the analysis should be conducted calmly based on the fault phenomenon to determine which of the faults occurred on several lines due to the connection of which lines. This will reduce the scope of the problem. For example, a camera with three variable lens image signal is normal, but the lens can not control, you do not have to check the video output line, but just check the lens control line on the line. In addition, connectors, especially BNC type connectors, are very high in the welding process and the connection and installation of video cables. If they are handled improperly, even if there are no problems in the commissioning and commissioning stages, problems occur after a period of operation. It is particularly worth pointing out that cameras with pan-tilt heads have a long time due to all-round movements, resulting in disconnection and breakage of connections that are common. Therefore, special attention should be paid to the connection of equipment and various lines in this case to meet the requirement of long-term operation.

3, the quality of equipment or components itself. In general, there should be no quality problems with carefully selected commercialized equipment or components.

Workaround: Even if a problem occurs, it often occurs after the system has been delivered and run for a long time. In addition to the quality of the product mentioned above, the most common problem is due to improper adjustment of the equipment. For example, the adjustment of the intercept after the camera is a very precise and precise job. Without careful adjustment, problems such as poor focusing or defocusing in various operations of the three-variable lenses may occur. In addition, whether the positions of some switches and adjustment knobs on the camera are correct, whether they meet the technical requirements of the system, the correctness of the encoder coding switch or other adjustable position settings directly affect the normal use of the device itself or affect the normal performance of the entire system.

4. Problems caused by incorrect connection between equipment (or parts) and equipment (or parts)

1) Impedance mismatch. If the video is connected to a monitor with a high impedance, there will be very bright images, jittery characters, or sometimes characters.

2) The communication interface or communication method is incorrect. This situation often occurs between a control host and a device such as a decoder or control keyboard that has a communication control relationship. This is mostly due to the fact that the selected control host and decoder or control keyboard are not products of one manufacturer. In general, different manufacturers use different communication methods or transmission control codes. Therefore, the same manufacturer's products should be used for the host, the decoder, and the control keyboard.

3) The drive capacity is insufficient or exceeds the specified number of device connections. For example, the number of main control keyboards and sub-control keys corresponding to the control host is regulated. Exceeding the prescribed amount will cause the system to work abnormally. Decoder pan/tilt working power power is lower than the actual pan-tilt, it can not drive the PTZ.

5, the failure of the PTZ. A pan/tilt is incapable of operation or cannot rotate at a short time after use. It is a common troubleshooting method for PTZ: In addition to the product quality factors, the appearance of this kind of situation is mainly caused by the following reasons; only the camera is allowed to be The head mounted (that is, the camera sitting on the upper part of the turntable) uses a hoisting method (ie, the camera is mounted under the turntable). In this case, the hoisting method leads to an increase in the operating load of the pan/tilt. Therefore, the use of the hoisting method will soon lead to damage to the drive mechanism of the pan/tilt, or even burn the motor.

The total weight of the camera and its protective cover exceeds the weight of the PTZ. Especially for PTZs that are used outdoors, the weight of the protective cover is often too large, and there is often the problem that the PTZ will not move (especially the vertical direction). The outdoor pan/tilt head is faulty or even damaged due to poor ambient temperature, low temperature, waterproof, and frost protection measures.

6. When the distance is too far, the keyboard cannot be controlled by the decoder to remotely control the camera (including the lens) and the pan-tilt: this is mainly because the control signal is greatly attenuated when the distance is too far, and the control signal received by the decoder is too large. Weakly caused. At this time, a relay box should be installed at a certain distance to amplify the shaping control signal.

7, the monitor image contrast is too small, light solution: This phenomenon, if not control the host and the monitor itself, is the transmission distance is too far or the video transmission line attenuation is too large. In this case, the line amplification and compensation device should be added.

8, the image clarity is not high, the detail is lost, serious color signal loss or color saturation is too small Solution: This is due to the loss of the high-frequency end of the image signal is too large, resulting in the basic loss of signals above 3MHz frequency of. In this case, either the transmission distance is too long and there is no amplification compensation device in the middle; or the distribution capacitance of the video transmission cable is too large; or the equivalent capacitance is concentrated in the transmission link between the core wire and the shielded wire. Caused.

9, tone distortion solution: This is a long-distance video baseband transmission mode prone to failure. The main reason is caused by the large phase shift of the high frequency band caused by the transmission line. In this case, a phase compensator should be added.

10, the operation of the keyboard failure solution: This phenomenon in the inspection connection is no problem, basically can be determined to operate the keyboard "dead" caused. The explanation of the operation of the keyboard, there are generally methods to solve the "crash", such as "whole machine reset" and other methods, this method can be used to solve. If it cannot be solved, it may be that the keyboard itself is damaged.

11. The host computer does not switch the image clearly. Solution: This kind of failure phenomenon is manifested in the screen after the selection is cut, the interference of other screens is superimposed, or the interference of the line synchronization signal of other images. This is due to the poor quality of the matrix switcher of the host and the lack of isolation between images. If a radio frequency transmission system is used, it may also be caused by the system's cross-talk modulation and excessive modulation.

A large-scale television monitoring system that operates in conjunction with anti-theft alarms is a high-tech and complex system. Although various kinds of failure phenomena may occur, as long as the quality of selected equipment and equipment is properly shut down and construction is strictly conducted in accordance with standards and specifications, generally no major problems will arise. Even if there is a problem, as long as the analysis and thinking is calm, “doing the right thing” does not blindly deal with the problem. It will solve the problem faster.

12, poor communication troubleshooting methods: the performance of the controlled pan/tilt or electric lens can sometimes be normal action, and sometimes can not (or delay) action, or stop after action, this is mainly due to the problem of communication lines. Check the RS-485 communication terminal matching resistance (120¦ ̧) on the decoder when confirming that the wiring is correct and the circuit is correct. Or disconnect the host interface and the far-end matching resistor, use a multimeter to measure the DC resistance RD of the terminal pin of the single communication chip and the DC resistance R2 of the communication port of the entire system, and compare it with the theoretical calculation (R2=R0/n, where n For the number of decoders connected in the entire system), if the difference is too large, it can be determined that there is a problem with the communication chip, and the problematic chip is found by the point-by-point elimination method. If the communication line has many branches, you can disconnect the branches to determine the approximate range of communication failures.