1756-EN2TXT Beginning of remote i/o

1756-EN2TXT A good 75ω terminating resistor should be added at the beginning and end of the remote i/o to absorb the excess energy of the signal at the end and to prevent causing signal reflection. When making the terminal joints of the cable, they must be standardised using the special tools provided by the supplying manufacturer. Coaxial cable and rio processor, rio adapter and the connection between the branch must use a special terminal connector, due to the number of more, so this work to ensure the reliability of the system communication is also very critical, any position of the cable joints do not do a good job, will affect the communication status of the entire system.

1756-EN2TXT Due to the existence of the above interferences, the communication between the 3PC CPU master station and the 3# remote station is intermittent. During the period of communication interruption, the 3#cylinder to mixing-13 belt in 3# station could not receive the operation information of mixing-3 belt, so the 3#belt was shut down by mistake, which caused the 3#cylinder to mixing-13 belt to stop in automatic sequence. When the communication was restored, the running information of the 3# belt was received normally, and the 3# cylinder to mix-13 belt started again automatically. As a result, the process equipment in this section frequently starts/stops automatically.

Measures taken by 1756-EN2TXT: After careful analysis, the author believes that although there are so many possibilities above, there are 2 main reasons for remote i/o system interference: frequency conversion system interference and system grounding. Therefore, the following measures are taken from these 2 aspects:

(1) Measures for frequency conversion system interference

Remote i/o coaxial cables and power cables and control cables are completely separated, separate laying, and all through the pipe laying; – cable routing as far away from the inverter as possible; – cable routing as far away from the inverter as possible.

Cable routing as far away as possible from the frequency converter and other sources of high-frequency interference.

-All the branch from the original plc cabinet installation to move away from the cabinet to the location of a separate installation, and special metal shielding box for shielding; -Sub-station cable length is uniformly taken as the length of the substation cable.

-The length of the substation cable is 3m long.