Catalytic Combustion Sensor is a sensor widely used in combustible gas detection. Its working principle is based on the combustion reaction of gas under the action of catalyst. The gas concentration is measured by detecting the heat change generated by combustion. The following is a detailed description of its working principle, characteristics and applications:

I. Working principle

1. Core structure

The sensor usually consists of two platinum wire coils, which serve as the two arms of the Wheatstone bridge:

Detection element (Active Element): The surface is coated with a catalyst (such as palladium, platinum, etc.) and exposed to the gas to be measured.

Compensation element (Reference Element): Encapsulated in an inert environment, not in contact with the gas, used to compensate for changes in ambient temperature.

2. Catalytic combustion reaction

When combustible gas (such as methane, propane, etc.) diffuses to the surface of the detection element, it reacts with oxygen under the action of the catalyst:

CH₄+2O₂  catalyst  CO₂+2H₂O+ Heat

The heat released by the combustion increases the temperature of the detection element, resulting in an increase in the resistance value of the platinum wire.

3. Signal output

The resistance difference between the detection element and the compensation element causes the bridge to be unbalanced, and the output is a voltage signal proportional to the gas concentration. After circuit processing, the concentration value is displayed.

II. Features

Advantages:

1. Sensitive response to most combustible gases (such as methane, propane, and hydrogen), linear output.

2. Simple structure, low cost, suitable for long-term continuous monitoring.

3. Good stability and long life (usually 3-5 years).

Limitations:

1. Depends on oxygen environment and cannot be detected under oxygen-deficient conditions.

2. Susceptible to catalyst poisoning (such as silicides, sulfides, halides, etc.).

3. High concentrations of combustible gases may cause sensor overload or damage.

4. No response to non-combustible gases (such as CO₂), low selectivity.

III. Main applications

1. Industrial safety monitoring

Combustible gas leak detection in petrochemical, natural gas pipelines, coal mines and other places.

Explosion-proof warning systems for tank areas, gas stations, and chemical plants.

2. Civilian fields

Household gas alarms (natural gas, liquefied petroleum gas).

Gas leak monitoring in kitchens and boiler rooms.

3. Special environments

Carbon monoxide and combustible gas composite detection in tunnels and underground parking lots.

Methane concentration monitoring in landfills.

4. Other scenarios

Exhaust gas analysis of gas turbines and internal combustion engines.

Combustible gas concentration control in laboratories or industrial processes.

IV. Precautions

1. Calibration and maintenance

Regular calibration (usually every 6 months) is required to prevent catalyst failure or drift.

Avoid exposure to environments containing toxic substances to extend sensor life.

2. Usage conditions

The operating temperature range is generally -40°C to 70°C, and excessive humidity may affect performance.

It is required to work in an environment with an oxygen concentration of ≥10%.

5. Comparison with other sensors

Electrochemical sensors: suitable for toxic gases (such as CO, H₂S), but with a short lifespan.

Infrared sensors (NDIR): highly selective and resistant to poisoning, but with a high cost.

Semiconductor sensors: highly sensitive, but easily affected by temperature and humidity, with poor stability.

    Catalytic combustion sensors occupy an important position in the field of combustible gas detection due to their reliability and economy, but they need to be combined with other technologies (such as infrared or electrochemistry) according to specific scenarios to achieve more comprehensive gas monitoring.

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