You are wanting to read a 12 volt current loops 4-20 mA loop I take it.
The 250 ohm resistor is a stunt you read the voltage across it to get the current readings.
You have to use some kind of stunt to take a reading so why not a 250 ohm?
I think I2V is " current to voltage" converter. I think the poster is objecting to the fact that a 4-20mA current loop will yield 1 volt at 4mA instead of 0 volts.
The convenience of a 0 – 5 volt signal instead of a 1 – 5 volt signal requires a lot more complexity than a simple resistor.
TI makes some current loop converters that provide the option of a 0-5v output.