Emerson DCS communication
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A beginner is seeking advice: a chiller on site cannot establish Modbus communication with the Emerson DCS system. How can one determine whether the issue lies with the signals at the site or with a faulty component in the DCS itself?
Don’t worry about hardware issues for now; check the communication parameters, the addresses being read, and so on. . . .
You can use modscan to scan and see if it can retrieve the data
First, use your own laptop to run a MODSCAN scan on-site to see if a connection can be established. If a connection is possible, then there’s nothing wrong with the device; if not, check the communication parameters. If those parameters are also fine but a connection still can’t be made, it’s likely that there’s an issue with the device. Once a connection is established, use the laptop to perform a MODSCAN scan in the cabinet room to see if a connection can be achieved there. If a connection is possible on-site but not in the cabinet room, it’s very likely that the cable is too long and causing signal attenuation, so a relay needs to be added. Only after ensuring that connections work fine both on-site and in the cabinet room should communication with the DCS be attempted