I have a vendor control panel with an Omron SYSMAC CP1L PLC connected to a Danfoss VFD via an unmanaged switch. A Red Lion CR 3000-7000 HMI is used to monitor and control the VFD
's speed manually or based on a process temperature. The HMI has two ethernet ports, one for internal machine control and another for the controls network communication. I would like to capture the historical VFD's speed data to be displayed in a graph. I'm not sure what OPC UA to use to accomplish this. There are Omron OPC UA's, but there aren't any Red Lion. I'm not sure what approach to take to read data from port 2 that's received by port 1.
From some quick googling, and some assumptions about system.
The red lion hmi is probably communicating to the danfoss vfd through modbus TCP. The redlion hmi can act as a modbus server, at least there documentation says so, through the additional ethernet port. This would require the vendor to program this in to the hmi if they already have not. I would ask the vendor if this is already configured.
If there is an extra port in the ethernet switch between the drive and the HMI I would connect to the drive and just monitor the correct register using modbus TCP. Now if there are more items you want to collect than just the information about speed form the drive I would look at the omron opcua server if it is also connected to the drive.