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Common methods in the maintenance process of weak current systems
The weak current system is currently in all aspects of building equipment and facilities. It can be an independent control system and can participate in the control of other equipment, becoming the core of automation control.
The content of the weak current system is very extensive and complicated, which brings certain difficulties to the use and maintenance of the weak current system. In order to maintain the weak electrical equipment and facilities, in addition to understanding the principle knowledge of each weak current system, there must be some operational skills. Mastering these skills can achieve twice the result with half the effort.
Several methods commonly used in the maintenance of weak current systems
First, the exclusion method
Exclusion is the elimination of the non-probable factors that cause the problem, to determine the possible factors, and then focus on the possible factors to solve the problem. The exclusion method must first proceed from the subjective point of view, determine what factors may affect the problem, and then analyze which are more likely to be dealt with.
The most common method of exclusion is to check the line condition. If the line is unreasonable, first consider whether there is a recent construction modification or renovation that causes the line to be interrupted during the transformation process. If not, it can be excluded by the exclusion method;
If the line is short-circuited, first consider whether the line is broken by the metal to cause the wire to be overlapped. Secondly, consider whether the line pipe is damaged by the skin line, and if not, it can be eliminated.
If the line transmission is unstable, when the time is up and down, it is necessary to consider whether there is strong electromagnetic interference, whether it is affected by strong electricity, and it can be eliminated if it is not.
Second, take the Chinese law
The operation method of taking the Chinese method is to disconnect from the middle of a line with multiple equipment points, and then check whether the fault is solved, so as to determine whether the fault is caused by which end of the line, and through continuous investigation, it can be finally Lock the faulty device or faulty line.
The Chinese method is often used to troubleshoot signal transmission faults or partial short-circuit faults on the power supply line. For example, a 485 signal line is connected to 30 devices. One or several of the devices have problems, or there is a problem with the line, causing the transmission to fail.
We have to troubleshoot such problems and use the Chinese method to find the problem quickly. Since 485 is a bus transmission, the transmission line at the intermediate point is disconnected, and the communication in the first half is still normal. If the fault still exists, the problem lies in the line or equipment in the first half, and the line in the first half is disconnected. At the end of the investigation, you can find the problem. Then the problem is solved after reconnecting the line.
Third, the comparison method
The comparison method is a method of determining the problem by referring to the situation of other normally working devices. In order to get the problem, you need to know the general situation of the problem first, and then take the factors that are not very certain to the normal working equipment to verify the normal data. The comparison method is often used to check the unstable factors of the equipment and check the power supply of the equipment. , wiring conditions, setup steps, etc.
When we are faced with faulty equipment and there is no equipment information at hand, the comparison method can quickly help us to find out the general situation. For example, we can use a multimeter to measure the working voltage of the normal equipment to judge whether the voltage of the faulty equipment is normal;
You can use the wiring method of the normal equipment to modify the wiring mode of the faulty equipment to determine whether the problem occurs due to irregular wiring.
You can use the setting parameters of the normal device to modify the setting parameters of the faulty device to determine whether the fault caused by the parameter is abnormally modified.
Fourth, the replacement method
The replacement method is to replace the faulty device and cable with normal equipment and cables to find the problem. The replacement method requires us to have a replacement or new product.
The replacement method is often used to eliminate equipment failures, which is simple and easy to solve. For example, when I found a control panel on the scene, there was already obvious burnt marks on it, so replacing the upper backplane would solve the problem directly.
The premise of this law is that the cause of the damage is known. For example, we have found that the equipment is dripping into the rainwater, and the damaged parts can be directly replaced after the waterproof treatment. Five, the change method
The change method is to replace the normal working equipment and cables with the abnormally working equipment and cables, so as to judge whether the fault phenomenon is transferred or not, to determine the cause of the fault. This method is often used to determine a fault that is not known to the cause, or when there is no spare equipment on site.
For example, when the access control device is authorized, the card is issued to the front controller. After the card is issued, the card of the A controller can work normally, but the card of the B controller cannot be normal, so it is difficult to judge whether it is a defect of the B controller itself, or When the B-authorization is down, the B controller is disturbed and the unsuccessful.
We use the swap method to verify that when this method is used, most of the replacement methods have already been used, and the results are still unsatisfactory. We directly adjust the A and B controllers. If the B controllers are working properly, the A controller is not working properly. The fault can be caused by line faults or interference. If the B controller is still not working properly, the A controller works normally. Yes, it must be a device failure.
In addition, to solve the problem that the camera of the monitoring system has no image and the detector in the fire protection system is falsely reported, the method of changing the method can be used to judge whether the front end device is damaged.
Five, plugging and unloading method
Is to unplug unnecessary working parts and cables, remember the connection position of the components and cables, plug in the faulty parts and cables first, and then plug in other components and cables in turn to judge the faulty parts and cables. Whether it is abnormally affected by other components and cables, to determine the cause of the fault.
This method is often used to determine the faulty component of an abnormal device and the abnormality caused by the load exceeding the load capacity of the device.
For example, the abnormality of the gate lift in the vehicle management system. The normal gate lift signal consists of several conditions, the normal card lift, the computer release, the manual button lift, the fire alarm signal, the anti-smash signal and so on.
Falling is induced by the induction coil. If the gate is lifted up in the process of falling, then there are many reasons. Judging these reasons, you can only keep the falling signal, and the rest of the lines are removed, then look Whether it can fall normally, if possible, plug in other terminals in turn, and restore other functions to see which part of the cause is abnormally raised.
End
The above methods are often used in the maintenance of weak current systems. In actual operation, one or several types are used at the same time, and then the naked eye is observed in the cooperation. It is easy to judge the problem by measuring with a multimeter.