Serial to Ethernet to PLC

I have some flow meters that have several options for outputting the flow data (i.e. 4-20mA, 0-10V, 0-5000Hz and RS-232). We are using the Lantronix Xpress DR+ to convert the serial data to ethernet. I know there is software built by manufacturers designed to interface with the various instruments that they build. If you are using a PLC, how would you pull the data from the instruments? There are multipule readings we would like to take (i.e. instantaneous flow, total flow, temperature, etc.).

May I know what type/vendor of flow meter are you using and the PLC that you wish to establish a connection?