How should programming be done to convert the modulus input directly into an analog output in the most effective way?
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We are using PLC templates from Schneider’s 140 series. There is a pressure value at the site that is fed directly into the analog input template, where its value is displayed in the control room. Since another DCS also needs to have access to this value, I want to avoid using an isolation device for two-way communication. I plan to write a program using the UNITY software on the lower-level device to convert this analog input value into an analog output signal, which can then be sent to the DCS as a 4-20 MA signal. How should this program be designed? It would be best if the program could be modified without shutting down the system.
Is it problematic to directly pass the analog input value to the analog output using the MOVE instruction?
It is not possible to modify the PLC program without shutting it down; only a good DCS system can allow programming while the system is running.
The Schneider UNITY we use allows for online modification and installation of programs, without the need to shut down the system. This is applicable only to minor modifications; for more extensive changes, the installation must be carried out in stages in order to make modifications without shutting down the system.