MQ5 Gas Sensor Indication of the signal output. has Dual signal output (analog output, and TTL level output). The TTL output signal is low. (When low output signal light, and can be conted directly to the microcontroller). It has 0 ~ 5V analog output voltage, the higher the concentration, the higher the voltage.Liquefied petroleum gas, natural gas, city gas,gives better sensitivity. It Has a long life and reliable stability with Fast response and recovery characteristics