Communication Current Loop TTL 20mA with S7-300

[mhi]

Hello, I want to establish communication between my weigher controller with PLC S7 315 DP so that the PLC can read the 'Actual Weight Value' from the weigher (already connect with load cell). The signal data which is produced by the weigher controller is 20mA current loop TTY type (see attachment for the weigher signal specification). Can anyone give/consult me such an idea on how to convert the 20mA current loop signal to RS 485/RS422 so I can use Profibus DP port to read the value? Thank you.