MQ2 LPG Butane Hydrogen Gas Smoke Detection Sensor for Arduino/Raspberry-Pi/Robotics

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 RM0703 have 6 pin, 4 of them are used to fetch signals, and other 2 are used for providing heating current.
Resistance value of RM0703 is difference to various kinds and various concentration gases. So, When using this components, sensitivity adjustment is very necessary. we recommend that you calibrate the detector for 1000ppm of LPG concentration in air and use value of Load resistance ( RL) about 20KΩ(10KΩ to 47KΩ).  When accurately measuring, the proper alarm point for the gas detector should be determined after considering the temperature and humidity influence.
The gas sensor works like a combustible gas sensor. It is sensitive to not just LPG but other flammable gases like Natural, Methane, Coal gas, butane etc. It works by comparing a change in resistance between two heated elements. One heated element is a reference that is isolated from the sample gas. The other element is identical except that it is exposed to the sample. 
Catalytic oxidation of the target gas contained in the sample causes an increase in heat and a corresponding change in resistance. The two heated resistive elements are part of a balanced Wheatstone bridge. The changes in resistance between these cause an imbalance in resistance and a change in current flow in the bridge that can be measured as a voltage.
The voltage can then be measured by an ADC and computed into a ppm value by a microcontroller for display.

FEATURES

APPLICATION
They are used in gas leakage detecting equipments in family and industry, are suitable for detecting of LPG, iso-butane, propane, LNG, avoid the noise of alcohol and cooking fumes and cigarette smoke.