Sensitive material of MQ-7 gas sensor is SnO2, which with lower conductivity in clean air. It make detection by method of cycle high and low temperature, and detect CO when low temperature (heated by 1.5V). The sensor’s conductivity is more higher along with the gas concentration rising. When high temperature (heated by 5.0V), it cleans the other gases adsorbed under low temperature. Please use simple electrocircuit, Convert change of conductivity to correspond output signal of gas concentration. MQ-7 gas sensor has high sensitity to Carbon Monoxide. The sensor could be used to detect different gases contains CO, it is with low cost and suitable for different application.

Overview:
1) Sensitive for carbon monoxide
2) Output voltage boosts along with the concentration of the measured gases increases
3) Fast response and recovery
4) Adjustable sensitivity
5) Signal output indicator

Specifications:
1) Power: 2.5V ~ 5.0V
2) Dimension: 40.0mm * 21.0mm
3) Mounting holes size: 2.0mm
4) Applications:
Carbon monoxide monitor
5) How to Use: In the case of working with a MCU:
VCC ↔ 2.5V ~ 5.0V
GND ↔ power supply ground
AOUT ↔ MCU.IO (analog output)
DOUT ↔ MCU.IO (digital output)