Methane CNG Gas Sensor MQ4?is a simple-to-use compressed naturalgas (CNG) sensor, suitable for sensing natural gas (composed of mostly Methane[CH4]) concentrations in the air. The MQ-4 can detect natural gasconcentrations anywhere from 200 to 10000 ppm.
This sensor has a high sensitivity and fast response time. Thesensor?s output is an analog resistance. The drive circuit is very simple; allyou need to do is power the heater coil with 5V, add a load resistance, andconnect the output to an ADC.