Which one is more susceptible to external influences: AI, AO, DI, DO, RTD, or TC?
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For signal lines such as AI, AO, DI, DO, RTD, and TC, the shielding protection should not be grounded at a single point; which of these is most susceptible to interference from external currents, voltages, electromagnetic waves, etc.? Ranked from greatest to least impact, I order it as TC>DO>DI>AI>AO>RTD! Thank you!
Now that DOs are all opto-isolated, how can they be interfered with?
When moving from the cabinet room to the site, if it is parallel to the high-current, high-voltage cables used in electrical systems, or if it is too close to them, interference can occur
Provide the instrument with its own enclosure, which should be sealed with a lid and grounded.
There is little point in arranging them this way; everything I’ve seen has not been affected by any interference. If there is any, it’s most likely due to improper grounding, and it also relates to the quality of design of the DCS terminal boards. We have used unshielded compensation wires in conjunction with a small number of electrical circuits for over a decade without any interference occurring
The DOs connected to MCC are the most susceptible to interference, as we use dry contacts; the 220V electrical secondary circuits run directly through cables, which can lead to electromagnetic induction and cause the relays to activate unintentionally. Therefore, it is necessary to use relays with higher resistance to interference
There’s no problem using the tray boxes designated for instruments
It is required to run a separate cable for each electrical DO and DI, or to install a 24V relay in the MCC so that the DOs become 24V rated. Worst-case scenario: DO/DI mixed cables + cables without overall shielding + no trunking, sharing the same trench as UPS cables. Given the current situation, it is recommended that you connect the DO contacts of the MCC downstream of the electrical KM contactor. (There is no L wire inside the cable, which reduces the interference voltage from the L wire on other circuits); give it a try. . . .
Doing sorting like this really makes no sense at all. Interference is random and is also closely related to construction.