Introduction to MQ-9 sensor:
The gas sensing material used in MQ-9 gas sensor is SnO2 with low conductivity in clean air. The conductivity of the sensor increases with the increase of carbon monoxide concentration in the air. The combustible gas methane and propane are detected at high temperature (5.0V heating) and the stray gas adsorbed at low temperature is cleaned. Using a simple circuit, the change of conductivity can be converted into the output signal corresponding to the gas concentration. MQ-9 gas sensor has high sensitivity to carbon monoxide, methane and liquefied gas. This sensor can detect a variety of gases containing carbon monoxide and combustibility. It is a low-cost sensor suitable for a variety of applications.