FOXBORO card FBM242 (RH916TA) module


RH916TA FBM242 Channel Isolated External Source DO

Category: SKU: FBM242 P0916TA Tag:
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A good grounding is an important condition to ensure the reliable operation of the PLC, which can avoid accidental voltage surge hazards. The grounding wire of the PLC is connected to the grounding terminal of the machine, with a cross-sectional area of no less than 2mm2 and a grounding resistance of less than 100 Ω; If an expansion unit is to be used, its grounding point should be connected to the grounding point of the basic unit. In order to suppress interference on the power supply, input and output terminals, a dedicated ground wire should be connected to the PLC, and the grounding point should be separated from the grounding point of the power equipment (such as the motor); If this requirement cannot be met, it is also necessary to achieve common grounding with other equipment and prohibit serial grounding with other equipment. The grounding point should be as close as possible to the PLC.

Redundant system and hot standby system
In certain systems in industries such as petroleum, chemical, and metallurgy, control devices are required to have extremely high reliability. If the control system malfunctions, it will cause production stoppage, significant waste of raw materials, or equipment damage, causing significant economic losses to the enterprise. However, solely improving the reliability of the control system hardware to meet the above requirements is far from enough, as there is a certain limit to the improvement of the reliability of the PLC itself. The use of redundant systems or hot standby systems can effectively solve the above problems.

1. Redundant control system
In a redundant control system, the entire PLC control system (or the most important part of the system, such as the CPU module) consists of two identical systems. Two CPU modules work in parallel using the same user program, with one being the main CPU and the other being the backup CPU; The main CPU is working, while the output of the backup CPU is disabled. When the main CPU fails, the backup CPU will automatically put into operation. This switching process is controlled by the redundant processing unit RPU, with a switching time of 1-3 scan cycles. The switching of the I/O system is also completed by the RPU.

2. Hot standby system
In a hot standby system, two CPUs are connected together through communication interfaces and both are in a powered on state. When the system malfunctions, the main CPU notifies the backup CPU to put it into operation. This switching process is generally not very fast, but its structure is simpler than that of a redundant system.