Structure and configuration of MQ-3 gas sensor is shown as Fig. 3, sensor composed by micro AL2O3 ceramic tube, Tin
Dioxide (SnO2) sensitive layer, measuring electrode and heater are fixed into a crust made by plastic and stainless steel
net. The heater provides necessary work conditions for work of sensitive components. The enveloped MQ-4 have 6 pin, 4
of them are used to fetch signals, and other 2 are used for providing heating current.