MQ-9 gas sensor module has high sensitivity to Carbon Monoxide, Methane and LPG. Sensitive material of MQ-9 gas sensor is SnO2, which with lower conductivity in clean air.  It makes detection by cycling high and low temperature, and detects CO when low temperature (heated by 1.5V). The sensor’s conductivity is higher along with the gas concentration rising. When temperature rises (heated by 5.0V), it detects Methane, Propane, combustible gas, etc  and cleans the other gases as it adsorbed under low temperature. MQ-9 usually pplied in domestic gas leakage detector, industrial gas detector, portable gas detector, etc. 
 
 
Wire Connecting Method of MQ9 Carbon Monoxide, Methane and LPG Gas Sensor Module:-
VCC - positive pole (5V)
GND - negative pole
DO - TTL switch signal output
AO - analog signal output
 
Specification of MQ9 Carbon Monoxide, Methane and LPG Gas Sensor Module:-
Input voltage: DC 5V
Power: 150mA
DO output: TTL digital 0 and 1 (0.1 and 5V)
AO output: 0.1-0.3V (relatively clean), the highest concentration voltage is about 4V.
 
Features of MQ9 Carbon Monoxide, Methane and LPG Gas Sensor Module:-
Suitable for home or factory gas leakage monitoring devices.
Have better sensitivity to Carbon Monoxide, Methane and LPG Gas.
High quality dual-panel design, with power indicator and TTL signal output instructions.
DO switching signal (TTL) output and AO analog signal output.
TTL output valid signal is low. (When the output low signal is on, it can be directly connected micro-controller or relay module.)
Analog output voltage: the higher concentration, the higher voltage.
Four screw holes, easy positioning.
Long life and stability, quick response and resume.
 
* Product Images are shown for illustrative purposes only and may differ from actual product.