4-20 mA is not a variable resistor... it is called "current loop" communication and it still remains popular for industrial sensor interfacing.
It's been discussed before... have a look here: http://arduino.cc/forum/index.php/topic,19613.0.html
4-20 mA is not a variable resistor... it is called "current loop" communication and it still remains popular for industrial sensor interfacing.
It's been discussed before... have a look here: http://arduino.cc/forum/index.php/topic,19613.0.html