Arduino 4-20mA sensor

By step

Sample of connecting a 4-20mA sensor to an Arduino through a simple shunt resistor. Also includes a capacitor for low pass filtering of noisy input signals.

void setup()
{
  Serial.begin(9600);
  pinMode(A0, INPUT);
  pinMode(4, OUTPUT);
  digitalWrite(4, HIGH);
}

void loop()
{
  int r = analogRead(A0);
  Serial.print("A0: ");
  Serial.println(r);

  if( r > 200 ) {
    digitalWrite(4, HIGH);
  } else {
    digitalWrite(4, LOW);
  }
  delay(100);
 }