int analogPin = A0;
int AnRd;

void setup() {
 Serial.begin(9600);
}

void loop() {
  AnRd = analogRead(analogPin);
  float voltage = AnRd/ 1024. * 5;
  float resistance = 2000 * voltage / (1 - voltage / 5);
  Serial.print(resistance);
  Serial.println(" Ω");
  delay(100);

}