Gravity analogue propane gas sensor (MQ6) For Arduino uses MQ6 probe to detect iso-butane, propane and liquefied petroleum gas (LPG). It is less sensitive with alcohol, cooking fumes and cigarette smoke. It can be used in gas leakage detecting equipment in consumer and industry applications. The sensitivity can be adjusted by the potentiometer. The output is proportional to the density of gas. Users can use analogue reading to read the data from this sensor. To ease the difficulty of using this sensor, a gravity Interface is adapted to allow plug&play. The Arduino IO expansion shield is the best match for this senor connecting to Arduino.