Current to Voltage Converter Schematic Question

[Charlie]

If it measures at 8V, then you have 32 mA, so your original spec that it would never go over 20 mA was wrong.
What exactly is the source of this current? If you tell us what you are trying to do, we can help more easily. The solution given to you assumed your source would be O.K. with a 250 ohm load in series - that might not be the case.

[tufail74]

It started with 4-20mA so a normal resistor will not provide 0-5V rather it would give 1-5V. This will decrease the accuracy to 20%.

it seems to me, it is a standard current signal of 4-20mA.

For this reason, you need to use op-amp. Have a look at the circuit.

[Charlie]

This will decrease the accuracy to 20%.

Actually, it decreases the dynamic range, and is easily compensated for without op-amps.