/****************************************
*   TGS8100 sensor    Arduino Uno
*****************************************/ 

int adval = 0; //ADC data
float sensor_r; 

void setup() {
 Serial.begin(115200);
 pinMode(A0, OUTPUT); //PULSE pin
}

void loop() {
 digitalWrite(A0, HIGH); //PULSE pin HIGH
 delay(1); //Wait until OUT stabilizes
 adval = analogRead(A1); //ADC 
 delay(1); //
 digitalWrite(A0, LOW); //PULSE pin HIGH
 if (adval != 0) {
 //((3.0 / (adval * 5.0 / 1024.0)) - 1)*10k ohm
 sensor_r = 6144.0 / adval - 10;
 Serial.println(sensor_r, 1);
 }
 else Serial.println("div 0 ");
 delay(998); // 
}