What Is a Gas Sensor?
A gas sensor is a sensor that detects the concentration of a specific gas (CO, LPG, smoke, alcohol, etc.) in the air. It's critical in safety and air-quality applications.
How Does It Work?
The most common type (the MQ series) uses a metal-oxide surface: when the target gas contacts the surface, the material's resistance changes. This change is converted to a gas amount. A heater is needed for the sensor to work.
Types
| Model | Detects |
|---|---|
| MQ-2 | Smoke, LPG, flammable gas |
| MQ-7 | Carbon monoxide (CO) |
| MQ-135 | Air quality (CO2, NH3) |
Where Is It Used?
Fire/smoke alarms, CO detectors, kitchen gas-leak warnings, industrial safety and air-quality monitoring.
Analog and Digital Output
MQ-series gas modules usually offer two outputs: analog (AO) gives a voltage proportional to the gas amount, and digital (DO) produces a present/absent signal when a set threshold is exceeded. Analog is used for precise measurement, digital for a simple alarm.
Common Mistakes
- Not waiting for warm-up: the sensor needs a few minutes of pre-heating for accurate reading.
- Skipping calibration: for absolute measurement it must be calibrated in clean air.
- Cross-sensitivity: an MQ sensor can respond to more than one gas; it isn't selective.
Frequently Asked Questions
Why does a gas sensor heat up?+
Which sensor does a CO detector use?+
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