Hello,
To make simple my project, I want to make arduino as two wire 4-20mA sensor. As I know many industrial sensor are using 2 wire 4-20mA signal.
I still not found yet the simple reference schematic.
May all of you have schematic reference about arduino as 2 wire current loop transmiter or arduino loop powered 4-20mA ?
Thank you
Regards
Sony
GOOGLE : Arduino as 4-20ma sensor
Here is a circuit for you, this is one of thousands.

A 250 Ohm resistor is all you need to interface a 4-20 mA sensor. In the circuit below, C1 and R2 are optional, but help protect the Arduino from transients and overvoltage. Output V2 is 1 to 5V.


Thank for your response.
Most of I search in google result are arduino as reader 4-20mA that is not what I mean.
Let's say I want to arduino as 2 wire 4-20mA temperature transmitter.
For clear understanding what I need maybe you can search as refferences with key words "2 wire transmitter"
Thanks
I still not found yet the simple reference schematic
You won't, because current loop transmitters are not simple. Just buy one.
Everything easy if just buy but it will make "brain always new" 