Ammonia Gas Sensor Code (PPM)

#define RL 1 //I only used 1K instead of 47K
#define m_136 -0.2519296225 //Enter calculated Slope
#define b_136 -0.2299293912 //Enter calculated intercept
#define Ro_136 9 //Enter found Ro value
#define MQ_sensor_136 A0 //Sensor is connected to A0

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

void loop() {
  float VRL_136; //Voltage drop across the MQ sensor
  float Rs_136; //Sensor resistance at gas concentration
  float ratio_136; //Define variable for ratio

  VRL_136 = analogRead(MQ_sensor_136)*(5.0/1023.0); //Measure the voltage drop and convert to 0-5V
  Rs_136 = ((5.0*RL)/VRL_136)-RL; //Use formula to get Rs value
  ratio_136 = Rs_136/Ro_136; // find ratio Rs/Ro

  float ppm_136 = pow(10, ((log10(ratio_136)-b_136)/m_136)); //use formula to calculate ppm

  Serial.println(ppm_136);
  delay(5000);
}