void setup() 
{
    Serial.begin(9600);
}
 
void loop() 
{
    float sensor_volt;
    float RS_gas; // Get value of RS in a GAS
    float ratio; // Get ratio RS_GAS/RS_air
    float concentration;
    int sensorValue = analogRead(A0);
    sensor_volt=(float)sensorValue/1024*5.0;
    RS_gas = (5.0-sensor_volt)/sensor_volt; // omit *RL
 
   /*-Replace the name "R0" with the value of R0 in the demo of First Test -*/
    ratio = RS_gas/0.23;  // ratio = RS/R0  
    concentration = pow(10,((-1.51)*log10(ratio)-0.39));//in mg/L
    Serial.print("alcohol concentration = ");
    Serial.println(concentration);  
    Serial.print("mg/L");
    Serial.print("\n\n");
    delay(1000);
}