Urgent: Please have an expert resolve the communication issue between PLC and DCS
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The factory has newly installed a set of desalination equipment, which comes with its own PLC that is installed on-site. However, the plant believes that three of these signals (one for flow rate, one for conductivity, and one for pH analysis) are particularly important, and it wants to transmit these three signals to the central control room for monitoring. How should it be implemented? ? Should it be a 4x2x1.0 multi-core cable, or some other method? ? Please ask an expert to solve it
It’s easy to implement – the PLC simply sends output signals to the DCS card nodes; no communication is required. The hard-wired node method is reliable
There are two options: 1. As mentioned above, divide the signal on-site into two paths – one going to the PLC under local control and the other going to the DCS; 2. Add an additional remote controller. Through the PLC’s upper-level communication interface, the data is transmitted to the host computer in the control room (via port conversion). Of course, the application software for the PLC needs to be installed for this to work.
If you just check it in DCS, communication is sufficient; but for applications with high reliability requirements, hard wiring is necessary.
There’s not much else to say; what was mentioned above covers it pretty well. It’s best to run cables to the DCS control room, but use more than 4 sets of cables – otherwise you’ll have to redo the wiring if one cable gets damaged in the future
The control is still implemented in the PLC; the DCS is merely used for display. In this case, it is sufficient to simply pull the communication cable; there is no need for hard wiring.
It’s such a simple thing – there’s no need for communication; just use a distributor to divide the signal into two paths
Modern signal isolators generally have multiple transmission functions, with one output for DCS and another for PLC
For communication cables, ordinary shielded network cables will suffice; if communication is to be utilized, the PLC interface can communicate with the DCS.
What is the concept of hard wiring? I’ve seen this term in several places, but I don’t quite understand it. Please advise
It is recommended to use communication methods; although this might not be easy, as it requires cooperation between the DCS and PLC systems. However, it’s possible that in a few days the workshop will again request control of the facility through the DCS, so it’s better to get it right from the start
Wired connection: As opposed to communication methods, it can be understood as a connection established between two instruments through cables, with signals being transmitted via current, voltage, and resistance. I agree with what was said above – having the communication setup in one step avoids the need to run wires later on.
There are many ways for DCS to communicate with PLCs, such as hard wiring or RS485 communication, but Modbus is more commonly used for data exchange. The Modbus protocol is a universal language used in electronic controllers. Through this protocol, controllers can communicate with each other, as well as with other devices via a network (such as Ethernet). It has become a universal industrial standard. With it, control devices manufactured by different manufacturers can be connected into an industrial network for centralized monitoring.
It is recommended to use communication methods, with the Modbus protocol
I’ve encountered the same problem as well; there is a solution among the methods mentioned above. For reliability reasons, it is still recommended to use the distributor method.