MQ-7

General Description:

The sensitive material of the MQ-7 gas sensor is SnO2, which has lower conductivity in clean air. It makes detection by method of cycle high and low temperature and detects CO when low temperature (heated by 1.5V). The sensor's conductivity increases along with the gas concentration rising. When high temperature (heated by 5.0V), it cleans the other gases adsorbed under low temperature. This is a simple electro-circuit that converts the change of conductivity to the corresponding output signal of gas concentration. MQ-7 gas sensor has high sensitivity to Carbon Monoxide. The sensor can be used to detect different gases containing CO, and it is low-cost and suitable for different applications.

Working Principle:

The MQ-7 gas sensor employs a tin dioxide (SnO2) based sensing element, heated for optimal performance. In the presence of oxygen, the sensor's surface is coated with oxygen ions, hindering electron flow and maintaining a high resistance state. When exposed to reducing gases, these oxygen ions are consumed, leading to a decrease in the sensor's resistance and enabling current flow. This change in conductivity is proportional to the gas concentration, allowing for the quantification of gas levels based on the sensor's output voltage.

Specifications:

1. Having an IC chip LM393 voltage comparator.
2. Operating Voltage (VDC) is 3V to 5V.
3. It has the signal output indicating LED.
4. Having dual signal output (analog and TTL output).
5. It is highly sensitive to CO.
6. Operating Temperature: -10°C to 50°C.

Applications:

1. Domestic gas leakage detector.
2. Industrial CO detector.
3. Portable gas detector.