#define RefVoltagePin A0
#define MessurePin A1
#define RefResistorVal 9790.0

void setup() {
  Serial.begin(115200);
}

void loop() {
  // put your main code here, to run repeatedly:
  double  Ref = analogRead(RefVoltagePin); //Um Spannung zu berechnen: analogRead(RefVoltagePin) * 5.0/1023.0;
  double  Messure = analogRead(MessurePin); //Umwandlung zu Spannung nicht nötig, kürzt sich weg
  double  Resistance = (Ref - Messure)/ (Messure/RefResistorVal);

  static double LastResistance;

  if(LastResistance != Resistance){
    Serial.print("Widerstand= ");
    Serial.print(Resistance,3);
    Serial.println(" Ohm");
    LastResistance = Resistance;
    delay(250);
  }
}