FOXBORO P0901VK

Description

FOXBORO P0901VK

All kinds of signal transmission lines connected to the PLC control system, in addition to transmitting effective signals, will always be invaded by external interference signals. There are two main ways of this interference: one is the power grid interference connected in series through the power supply of the transmitter or common signal instrument, which is often ignored; The second is that the signal line is interfered by the induction of space electromagnetic radiation, that is, the external induction interference on the signal line, which is very serious. The interference introduced by the signal will cause the I/O signal to work abnormally and the measurement accuracy will be greatly reduced, and in serious cases will cause damage to the components. For the system with poor isolation performance, it will also cause mutual interference between signals, cause common ground system bus backflow, and cause logic data change, misoperation and crash. The number of I/O module damage caused by signal introduction interference in PLC control system is quite serious, and there are many system failures caused by it.

Interference from chaotic grounding system

Grounding is one of the effective means to improve the electromagnetic compatibility (EMC) of electronic equipment. Correct grounding can not only suppress the influence of electromagnetic interference, but also suppress the outward interference of equipment; On the contrary, the wrong grounding will introduce serious interference signals and make the PLC system unable to work normally. The ground wire of PLC control system includes system ground, shielding ground, AC ground and protection ground. The disturbance of the grounding system chaos to the PLC system is mainly caused by the uneven distribution of potential at each grounding point, and the existence of ground potential difference between different grounding points, which causes the ground loop current and affects the normal operation of the system. For example, the cable shielding layer must be grounded at one point. If both ends A and B of the cable shielding layer are grounded, there is a ground potential difference, and there is current flowing through the shielding layer. When abnormal conditions and lightning strikes occur, the ground wire current will be greater.

In addition, the shielding layer, the grounding wire and the earth may form a closed loop. Under the effect of changing magnetic field, there will be induced current in the shielding layer, which will interfere with the signal loop through the coupling between the shielding layer and the core wire. If the system grounding is confused with other grounding, the generated ground circulation may produce unequal potential distribution on the ground wire, affecting the normal operation of logic circuit and analog circuit in PLC. The logic voltage interference tolerance of PLC operation is low, and the distribution interference of logic ground potential easily affects the logic operation and data storage of PLC, resulting in data confusion, program flight or crash. The distribution of simulated ground potential will lead to the decline of measurement accuracy and cause serious distortion and misoperation of signal measurement and control. 1C31129G03 Technical parameters

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