Fixed name

README.md

@@ -13,7 +13,7 @@ This is a unified library to use sensors MQ: 2, 3, 4, 5, 6, 7, 8, 9, 131, 135, 3
 #define pin A0 //Analog input 0 of your arduino
 #define type "MQ-4" //MQ4
 #define ADC_Bit_Resolution 10 // For arduino UNO/MEGA/NANO
-MQUnifiedsensor MQ309(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type); //Example if sensor is MQ4 on Arduino UNO board
+MQUnifiedsensor MQ4(placa, Voltage_Resolution, ADC_Bit_Resolution, pin, type); //Example if sensor is MQ4 on Arduino UNO board
 MQ4.setRegressionMethod("Exponential"); //_PPM =  a*ratio^b
 MQ4.setA(1012.7); MQ4.setB(-2.786); // Configurate the ecuation values to get CH4 concentration
 MQ4.setR0(3.86018237);