Can two devices read the value of a meter via 485?
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There is currently a steam metering secondary instrument that displays and outputs four parameters: temperature, pressure, flow rate, and cumulative flow rate. The output signal type is RS485. Both Plant A and Plant B require this data. Plant A requires that the 485 signal be converted into a network signal using a 485-to-TCP module, and then transformed into an optical signal via an optoelectronic converter. It is transmitted via optical cable to Plant A and connected to the TCP communication module of Plant A’s DCS. Plant B’s DCS has a 485 communication module. The communication cable is not long either. Can the 485 communication cable from Plant B be connected in parallel to the instrument’s 485 communication interface? Can two hosts read from one slave?
Modbus SLAVE can only connect to one Master, whereas an Modbus TCP slave can support communication with up to 4 Modbus TCP Masters simultaneously. Since you have already switched to MODBUS TCP at the site, you just need to add a module that converts MODBUS TCP to MODBUS at Plant B.
Does your secondary meter have only one set of 485 outputs?