Sheet Arduino 4

String unit = "ohm";
String unitC = "A";
unsigned long Rzero;
int VD;
float current;
float voltage = 5.09; //Voltaggio esatto Arduino 5.09V
float resistance = 0.0; //Resistenza da individuare
float tResistance = 0.0; //Resistenza totale

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
}

void loop() {
  // put your main code here, to run repeatedly:
  pinMode(2,INPUT);
  pinMode(4,INPUT);
  pinMode(7,INPUT);
  pinMode(8,INPUT);

  Rzero=391000;
  pinMode(2,OUTPUT);
  digitalWrite(2,HIGH);
  delay(100);
  VD = analogRead(A0);
  resistance = Rzero;
  pinMode(2,INPUT);

  if(VD<105){
    Rzero = 45800;
    pinMode(4,OUTPUT);
    digitalWrite(4,HIGH);
    delay(100);
    VD = analogRead(A0);
    resistance = Rzero;
    pinMode(4,INPUT);
  }

  if(VD<105){
    Rzero = 4650;
    pinMode(7,OUTPUT);
    digitalWrite(7,HIGH);
    delay(100);
    VD = analogRead(A0);
    resistance = Rzero;
    pinMode(7,INPUT);
  }

  if(VD<105){
    Rzero = 466;
    pinMode(8,OUTPUT);
    digitalWrite(8,HIGH);
    delay(100);
    VD = analogRead(A0);
    resistance = Rzero;
    pinMode(8,INPUT);
  }

  float RX = VD*Rzero/(1024-VD);
  unit = "ohm";
  current = voltage/(RX+resistance);
  unitC= "A";

  if(RX>1000000){
    RX = RX/1000000;
    tResistance = (RX+resistance)/1000000;
    current = voltage/tResistance;
    unit = "Mohm";
    unitC = "μA";
  }else if(RX>100000){
    RX = RX/1000;
    tResistance = (RX+resistance)/1000;
    current = voltage/(tResistance/1000);
    unit = "Kohm";
    unitC = "μA";
  }
  else if(RX>1000){
    RX = RX/1000;
    tResistance = (RX+resistance)/1000;
    current = voltage/tResistance;
    unit = "Kohm";
    unitC = "mA";
  }

  if(VD>1020){
    Serial.print("Lettura non significativa");
    Serial.println();
  }else{
    Serial.print(RX,2);
    Serial.print(unit);
    Serial.println();
    Serial.print(current,2);
    Serial.print(unitC);
    Serial.println();
  }
  delay(1000);


}