4-20mA sensor interfacing circuit

The above circuit is for interfacing a 4-20 mA sensor and the functionality is as below:

• Sensor is powered by +5V
• The sensor used have the mechanism to produce current between 4-20 mA which is why it is called 4-20 mA sensor
• The current that flows into the circuit need to be converted to a voltage for measuring it for which 100 ohms resistor is used
• The resistor must be selected such that the voltage developed is within the measurement range of microcontroller
• The voltage developed has to be connected to a Analog pin of Microcontroller 
• The voltage however is not directly connected to Microcontroller but a opamp voltage follower is used in between
• Voltage follower has high input impedance and low output impedance which meant it acts as a matching device thus helping not to load the sensor directly resulting in erroneous measurement