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CCTV monitoring system failures and common solutions

    

In a monitoring system into the debugging stage, the stage of trial operation and delivery, all possible kinds of failure phenomenon, the phenomenon of these failures or not functioning properly, or system can not design requirements of the technical indicators, or a whole Performance and quality is not satisfactory, some of the so-called "soft illnesses." These problems for a monitor for a project, particularly for a complex, large-scale monitoring project did not say, is inevitable. Problems, trying to solve these problems, the engineering and technical personnel of the obligations and responsibilities.

In a monitoring system, the emergence of many problems in the commissioning and trial operation stage. Trial operation has been delivered and acceptance of the system, in general, a short period of time should not be a problem. Even if the system in use there is a problem, often in the quality of equipment or construction quality (especially the transmission part of the construction quality). Below on a number of the more common failure to provide to the readers as a reference.

7.1 caused by equipment and components or fault and that the solution

In equipment (or components) shall be required before the installation of debugging, electricity and other experimental work. Nevertheless, because in the process of installing some reason, the equipment (or components) are also common problems.

A, the power supply caused by incorrect equipment failure. Power incorrect generally have the following several possibilities: power supply lines or supply voltage is not correct, not enough power (or a supply line of the road enough diameter, buck too large, etc.), power supply system's transmission lines in short circuit. Open circuit, such as over-voltage transient. Especially because of error or an instant power supply over-voltage equipment caused damage to the situation from time to time.

B, for some lines, particularly with the equipment phase grounding line handled properly, a circuit, short circuit, the line between bad insulation, wiring and other errors led to equipment (or components) damage to property or decrease damage to the equipment itself has not However, the phenomenon is a reflection of the equipment or body parts.

As some equipment (such as with three variable lens camera and PTZ) there are many connections, often handled properly, there will be the issue. Especially the poor quality of some of the connector, the connection of the poor, there is a common cause of the problem. In this case, the phenomenon should be based on failure to stay calm in the analysis, judgement in a number of lines on the lines of what is due to problems connected to a kind of fault phenomenon. This would appear to narrow the scope of the problem. For example, one with three variable lens camera image signal is normal, but the lens can not control, do not have to check video output lines, and as long as the check-line on the Line of Control. In addition, the connectors, especially BNC-type joints, welding technology, video-link to install the technology requirements are very high, if handled properly, even if the trial operation stage of commissioning and no problems, but after running for some of the problems . Of particular note is that the PTZ with a video camera in all directions because of the campaign, a long time, resulting in the loss connection is common. Therefore, we must pay special attention to this situation equipment and various lines of connection should be in line with the requirements of running a long time.

C, equipment or parts of their own quality problems. In general, has carefully chosen the commercialization of equipment or components should not be a quality problem. Even if there are problems, often in the system has been delivered and running after a very long time.

In addition to the above-mentioned problem of the quality of their products, the most common is due to equipment issues arising from the improper adjustments. For example, cameras after the intercept requirements of the adjustment is a very precise and meticulous work. If not carefully adjusted, there will be bad or focus in the three variable-operation in various defocusing, and other issues. Another camera on some switches and adjustment knob position is correct, whether the system's technical requirements, decoder code switch or other adjustable positions set the correct or not the equipment itself will directly affect the normal use or affect the normal performance of the system as a whole.

D, equipment (or components) and equipment (or components) a link between the problems arising from incorrect. This problem, generally occur in the following areas:

a, impedance do not match, such as video to a high resistance to the impedance monitors, the image will appear very bright, jitter or characters appear when the characters sometimes without.

b, communication interface means of communication or not. This situation often occurred in the control console and decoders, such as a keyboard or control communications between the control devices. Most of this is due to choose the host and control decoders or control of the keyboard, and so is not a manufacturer of products caused by. Generally, different manufacturers used by the means of communication or transfer of control codes is different. Therefore, the host, decoders, control the keyboard, and other manufacturers should use the same products.

c, or lack of ability to drive beyond the prescribed number of connected devices. For example, the control console by the corresponding control vice-key keyboard and the number is provided. Exceeds the number will lead to system is not working properly. Decoder PTZ work Power PTZ lower than the actual, can not drive on the PTZ.

7.2 failure of the transmission system analysis and solutions

TV monitoring of the transmission system, or commonly used mainly to video transmission. Limited space, only below under way video transmission failure in the analysis and proposed some solutions.

a, video transmission, the most common failure is 50 weeks in the frequency interference. In the form of monitors on the screen there was a black or white bar bar, and slowly rolling up or down. This phenomenon is mostly produced by the system to bad roads and the introduction of a 50-week frequency interference (AC interference) caused by.

Needs mentioning that, sometimes because of the camera or control console ( the power of bad (or partially damaged) will be such a failure of (sometimes in two black bars or white bars), so the analysis Such failure phenomenon, a failure to distinguish between the two different reasons.

To distinguish the question of power is still the issue of the loop, a simple method is to control the host, the only access to a nearby power no problem with the camera output signal, if the monitors did not appear on the phenomenon of interference , Then control console no problem. Next available a portable monitor nearest to the camera in front of the video output and a video camera seized one by one, in order to find whether it has the power problems interfere with the camera. If, for processing. If not, it is interference from the loop, and other reasons.

b, on a grainy monitor the interference. The emergence of such interference, the minor will not be inundated when the normal image, while serious, will not be able to watch the images (or even destruction of sync). This failure is the cause of more than complicated. Generally have the following several reasons:

Video of the poor quality transmission lines, especially the poor performance of shielding (shielding network is not very good quality of the copper wire network, or shielding a network of thin and ineffective shield). At the same time, such video-line resistance is too large, resulting in a larger signal attenuation of the reasons for failure is also increasing. In addition, such video is not characteristic impedance of the 75 Ω, and beyond the parameters of the distribution is also a failure of one of the reasons.

This cause of the malfunction, is difficult to judge, because the light of the judgement after completion of construction (cabling has been completed), it difficult to change lines, and solutions. Therefore, the selection comply with the standards and requirements of the video cable is required to guarantee. Must not consider the money to buy because of the poor quality of the video cable, or endless trouble.

As the interference phenomenon is not necessarily bad and the video line of the fault, the judge is to accurately and carefully. Only when the exclusion of other possible only after the video line to consider the perspective of non-performing. The judgement is in the exclusion of other possible reasons for this failure, conditional, the remaining of this video cables (if not surplus, but in the system interception of a section of the cable) to the inspection department to detect . Failed test results, can determine the quality of cable is a problem. If this is the cable quality, the best way of course all of this is to replace all the cables, change to meet the requirements of the cable, which is completely the best way to solve the problem.

Not very serious interference in the circumstances, may try to take power through purification, online UPS to connect the power supply system as a whole the way, can often reduce or eliminate the basic interference. However, this method will sometimes because of space systems around the different signals and ineffective or sometimes effective, sometimes regardless of use.

As the power supply system is not "clean" and the cause. Power is not mentioned here, "clean" means, in the normal power supply (50 weeks of the sine wave) superimposed on the signal interference. This power on the signal interference, and more from the power grid in the use of SCR equipment. Particularly the high current and high voltage SCR equipment, power grids on the pollution is very serious, which led to the same power grid in power do not "clean." For example, the power grid in the high-power FM SCR speed devices, silicon-controlled rectifier devices, AC-DC transform SCR devices, and so on, will the power generated pollution.

This solution is relatively simple, as long as the entire system or used purification online UPS power supply, we can basically be solved.

Has a strong system near the source of interference. This can be achieved through the investigation and understanding and be judged. If this is the reason, a solution is to strengthen the shield camera, video and cable channels for ground handling.

c, as the core video cable line and shielding net short circuit, open circuit caused by the fault. This failure is in the form of the performance monitor on a deeper than the chaos of the large area of Netted interference, as well as the destruction of all images, Xingbu Cheng image and synchronization signal. This situation appears in more than BNC connector or other types of video on the joints. As long as carefully check each of these joints, you can solve the problem.

Such failure phenomenon It is also easy to judge, that such failure phenomenon occurs, is often not the whole system of all signals are the problem, but only in those joints bad Lushuo on.

d, due to the characteristic impedance transmission lines do not match the fault caused the phenomenon. The manifestations of this phenomenon is the on-screen monitors in the number of distance equal to the  interference, jamming signals in the frequency is basically the whole trip frequency several times. This is due to the characteristics of video transmission line 75 Ω impedance is not a result of the impedance mismatch. If you use the oscilloscope to watch images of the wave interference, will find that the first line of sync after shoulders, superimposed with a higher rate of the line-frequency harmonics Zhendang Bo, is that the resulting interference. Through the wave of video analysis and quantitative measurement of the cable, but also found that the resistance does not meet the requirements of video cable, and its distribution parameters is also not meet the requirements, in fact impedance mismatch This is also one of the reasons why. Therefore, it can be said that this interference is generated by the video cables and distribution of anti-Yam parameters do not meet the requirements arising from the comprehensive. This generally rely on the settlement of the issue "before-series connection resistance" or "end to resistance and" the means to solve. Here it is worth noting that in the video transmission distance is very short-term (usually less than 150 meters), using the impedance mismatch and distribution parameters too much video cables will not necessarily appear above the interference phenomenon. Therefore, the difference between a great distance transmission systems, analysis of this phenomenon when the fault will not be a short distance without interference confused.

Address these problems in the fundamental way is to buy video cable, we must ensure quality. When necessary, to conduct random testing cable.

e, due to the introduction of the transmission line space radiation interference. Such interference in the selection, mostly because of the transmission system, the system or central control room near the front have a stronger, higher frequency of space radiation sources. This solution is a system established, should understand the surrounding environment, try to avoid as far as possible away from the radiation source or the other way when unable to avoid the radiation source, front and center on strengthening shielding devices, The transmission line pipe and the pipe used good grounding.

7.3 Other fault phenomenon

a, PTZ fault. PTZ in the use of a soon after not working well or simply can not turn, is PTZ common fault. This situation appears to remove the product quality factors, mainly caused by a variety of reasons;

Will only allow cameras are installed (that is, the camera sitting in the upper part of PTZ turntable) PTZ, when used in the use of the lifting of the way (to be installed in the camera PTZ the table below). Under such circumstances, the approach led to the lifting operation PTZ load up, it will soon lead to the use of PTZ damage to the transmission mechanism, or even burning motor.

Cameras and shields, and so the total weight of the load-bearing more than PTZ. Especially the outdoor use of PTZ, often shields the excessive weight, often PTZ to be fixed (in particular the vertical direction to the fixed).

Outdoor PTZ for environmental temperature is too high, too low, waterproof, antifreeze measures and failure or even bad damage.

b, distance too far, the operation of the keyboard can not be decoders for the camera (including the lens) and PTZ a remote control. This is mainly because the distance too far, too much control signal attenuation, the decoder received from the control signal is too weak. At this time should be within a certain distance on the installation of relay boxes to plastic surgery to enlarge the control signals.

c, monitors the image contrast is too small, image desalination. This phenomenon is not as monitor and control console itself, transmission distance is too far or too much attenuation video transmission line. In such circumstances, should join the line to enlarge and compensation devices.

d, sharpness of the image is not high, some details of the loss, there will be serious when the color signal is lost or spent on the color saturation. This is because high-frequency signals in the image-loss is too large, resulting in more than 3 MHz frequency signal to the basic loss. This situation, or transmission distance too far, and to enlarge the middle without compensation device; or video transmission lines and distribution capacitors too large or because of transmission links in the transmission line in the core line and shielding line between a focus on the distribution of equivalent capacitance Caused.

e, color distortion. This is the long-distance transmission of video-based approach to the failure of the phenomenon. Main transmission line caused by the high-frequency signal phase shift caused by too much. This phase should be for compensation.

f, keyboard operation failure. This phenomenon connected with the inspection issue, can basically be defined as the keyboard operation, "Dead" to it. That the operation of the keyboard, normally have to solve the "Dead" approach, such as "equipment reduction" method, you can use this solution. If can not, on the keyboard itself may be damaged.

g, the image of the host switch is not clean. This performance is the fault of the election, after cutting the screen, superimposed a picture of the other interference, or other images to sync signal interference. This is because the host switch matrix of bad quality, not images of isolation between the demands created by.

If using a radio frequency transmission system, the system may also be the hand-interference and mutual modulation modulation caused by too much.

A large-scale, anti-theft alarm linked with the operation of the television monitoring system, is a high technology content, a complex system. Although the phenomenon of various failures may arise, but as long as the good by the optional equipment and the quality of equipment, in strict accordance with standards and norms in the construction, is generally not a big problem. Even if there are problems, as long as calm analysis and reflection, "the right remedy," not to blindly and the dumping of the demolition, it would quickly resolve the problems.

h, bad communication failure

Controlled performance for the PTZ or electric-action can sometimes be normal, and sometimes it can not (or delay) action, or action can not stop after this is the main communication lines in question. In recognition wiring accurate, correct lines of circumstances, check decoder on the RS-485 communication terminals match Resistance (120 Ω). Or disconnect the host interface and the most remote match resistance with a multimeter measurement of a single-chip communications-foot DC Resistance RD and the whole system of communications port of DC Resistance R2, and theoretical calculations to compare (R2 = R0 / n, where n For the whole system and then by the number of decoders), if the difference is too large, communications chip can be recognized as a problem and, through case-by-point rule out the possibility of a problem to find the chip. If a lot of slip road communication lines, you can disconnect the slip road to determine the approximate breakdown of communication.


　

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