PLC failure maintenance method

Along with the instrument and meter plant to look at; Due to the PLC control system is composed of a variety of equipment, installation of components as a whole, therefore, to do a good job in the safety of the whole system is only the first steps to explicitly control system fault detection, to strict screening of potential risk factors. Fault detection of PLC control system has the following four steps: one is to test the system on the basis of operation. First of all, on the basis of the system is relatively simple function for screening, such as view the system input and output function is normal, after complete based on system testing, in order to determine the initial phase of the system for fault; Second, the fault detection. On the basis of complete system after testing, if don't find fault, then all possible failure for the entire control system in the corresponding detection, to determine the safety of the system: third, fault isolation. After check out the system failure, to take the initiative to isolate fault; Four is failure evaluation and decision making. In view of the failure found, must carry on the thorough analysis, and judgment, and take the corresponding measures and evaluation. Fault detection method 1, appearance test first, can undertake overall appearance inspection for PLC system, trying to identify risk factors in the system in a timely manner. For example, for some have entered the loss of components to be replaced regularly; What have found on the system will cause safety factors to take corresponding measures. Therefore, only familiar with and knowledge of the various modules of the system, can truly grasp system failure may be the distribution of the area. 2 macroeconomic diagnostics, diagnosis method, on the basis of the existing work experience refers to identifying to check whether it is caused by improper operation of fault, which based on the system failure surface to determine the cause of the failure and area, check whether the power supply in time to open, the line is correct, the scene is specification, etc. 3, microscopic test micro agglutination test system mainly for the fault may occur in the software design, once appear this kind of circumstance, check the system hardware design and software design. For example, for the fault detection of the CPU. CPU fault is mainly manifested in the corresponding LED lamp is not bright or CPU unit downtime. When this happens, consider the following three main reasons: one is due to noise power doesn't work; 2 it is inside the CPU bus malfunctioned electrical components; 3 it is CPU control program is missing. Therefore, for the CPU software fault, will be according to the actual situation of each region to determine the specific reason for the failure. If the fault is caused by noise, if you need to restart your CPU to reboot your system is the problems within the program, then reload or modify the system program. 4, dynamic test in the whole control system work, due to various parts of components and the controller itself is in operation, as a result, these controller and components may occur anywhere failure, therefore, in order to detect the cause of the failure in time, it is necessary for the system to conduct a comprehensive and dynamic detection. System dynamic testing can be done by design software, through the whole process of software real-time monitoring to detect failure. Their specific work has the following three steps to complete: one is the input test. This part is mainly on each switch outside the system quantity feedback signal detection and conversion function; The second is the state transition system. This part is mainly to achieve signal detection, and history of each area in the system state aspect: the content of the three is the output. This part is mainly based on the current state of the system to determine the status of the control signal. PLC control system in a monitoring cycle through the implementation of the 3 steps in turn, can realize the full control of the system. The original source. Instrument control engineering web editor: Katie instrument equipment factory