Grove - Gas Sensor(MQ-2)：Combustible Gas Smoke [middle sensitivity]
Grove - Gas Sensor(MQ-3)：Alcohol and Benzine [HIGH sensitivity] Long warmup
Grove - Gas Sensor(MQ-5)：LPG, Natural Gas, Town Gas [high sensitivity]
Grove - Gas Sensor(MQ-9)：LPG, CO, CH4 [low sensitivity]

Note - Gas sensor need to be heated, first minute the data is incorrect.
