[PIC] 4-20ma input to pic

[MODCHIP]

hello every one

i m trying to understand a small circuit for interfacing 4-20ma to a pic

i think after this circuit i must calculate the adc inverse that means for 4ma i wil have around 4.44v

and for 20ma i will have around 0.88v is that true

and is the amplifier here work as a comparator or not

and how to calculate the 100R resistance

thank you for help

 

[FvM]

The circuit is bad in several regards and not guaranteed to work with LM324 at all due to minimal specified sink current of 12 mA. The purpose of the 510 ohms resistor is mysterious and would cause failure of the circuit with many 4-20 mA drivers.

I also can't reproduce your calculations.

My first choice for a 4-20 mA converter would be a 250 ohm shunt.

 

[MODCHIP]

thank you for the replay

i alredy have this idea about the circuit
and i found it in a board with pic microcontroller and my project is about to replace this board by a new one

i just asked to undrestand how the conceptor of this bord work and i add that at the and of the AOP
there is a 5.1v zener diode and a 10uf capacitor

i geusse the zener diode is to protect the input of the pic

but i also with the project that i will made new one

also i will fix some of this board with lm324

so i m trying to undrestand the hole work and also i think the 100R resistor is not the real value