RS485 to TCP/IP Converter

I want to get some sensors readings on my web (or local network) software so I use process controller with RS485 output and serial to TCP/IP converter.

So my question, can the converter act as Master to slave controllers? or not? How would I send the query to get the sensor reading?

P.S. i try to avoid using PLC or other master controllers since I only read data.

Any references or tutorials would be appreciated!