Two 4-20 mA masters/readers for one sensor
You can place a second receiver on an industrial 4-20 mA loop. The key to success is to ensure that the added receiver presents a minimal voltage drop across its current loop terminals.

For example, a 47 ohm resistor usually is not a problem as this represents only a ~1 volt drop. If your secondary monitoring device shares no grounds with the remainder of the system, you can then directly feed this into your ADC. If grounds are shared then a differential amp or an opto isolator is required.

Alternatively, if the PLC has communications capabilities, you may find that querying the PLC through OPC UA or similar, will net the value of the current loop.