Semiconductor MOS Gas Sensor:Working,Advantages,disadvantages,Manufacturers

Introduction : A Semiconductor Gas Sensor, often called a Metal Oxide Semiconductor (MOS) gas sensor, is one of the most commonly used technologies for detecting gases such as methane, carbon monoxide, hydrogen, LPG, and volatile organic compounds (VOCs). MOS gas sensors are widely used in industrial safety systems, air quality monitoring, home appliances, automotive applications and IoT devices.

Semiconductor MOS sensor Working principle

The semiconductor MOS sensor works based on chemiresistive effect of a metal oxide semiconductor. At operating temperature of about 200–400 degreeC, oxygen molecules adsorb onto the MOS surface and capture free electrons. This increase resistance. Let us understand working of semiconductor MOS sensor.

• The sensor has heater which keeps the MOS surface hot.
• In the clean air, oxygen adsorbs on the surface and forms O-ve ions. This increases resistance.
• When actual condition when methane (CH4) is present; it reacts with these oxygen ions and releases trapped electrons back to the MOS. This decreases resistance.
• The change in resistance is measured and it is proportional to methane concentration.
• The output is measured in resistance (Ohm) or voltage (via a load resistor) which is mapped to ppm for methane gas (CH4) to be measured.

Advantages of Semiconductor MOS sensor

Following are some of the benefits of Semiconductor MOS sensor.

1. It is available in low cost.
2. It is small and compact in size.
3. It offers fast response time.
4. It has simple driving circuit.
5. It is available in both analog and digital modules.

Disadvantages of Semiconductor MOS sensor

Following are some of the drawbacks of Semiconductor MOS sensor.

1. It is non selective i.e. cross-sensitive to many gases.
2. It requires heating. Hence it consumes more power which is not ideal for battery devices.
3. It is affected by humidity and temperature. It requires compensation.
4. It is not highly accurate. Hence it is suitable for detection/alarms, not precise ppm measurement.
5. It offers limited lifetime; typically 2 to 5 years.

Manufacturers

Conclusion: With their balance of affordability, sensitivity, and versatility, semiconductor MOS gas sensors remain an essential choice for both consumer and industrial gas detection systems.