Carbon Dioxide Sensor

A gas sensor measures the concentration of gas in its vicinity through direct interaction with the gas. The sensor identifies gases by measuring the current discharge in the device.

The following are the different types of gas sensing technologies:

• Electrochemical gas sensors
• Optical gas sensors
• Calorimetric gas sensors
• Acoustic wave based gas sensors
• Metal oxide-based gas sensors.

A carbon dioxide sensor measures gaseous carbon dioxide levels by monitoring the amount of infrared (IR) radiation absorbed by carbon dioxide molecules. Measuring carbon dioxide is critical in monitoring many industrial processes and indoor air quality.

Types of Carbon Dioxide Sensor

The following are two major types of carbon dioxide sensors:

Nondispersive Infrared (NDIR) Carbon Dioxide Sensors

NDIR sensors are spectroscopic sensors that detect carbon dioxide in a gaseous environment by its characteristic absorption. It includes an infrared detector, an interference filter, a light tube and an infrared source. The gas is either pumped or diffused into the light tube, and the electronics measure the absorption of the wavelength of light.

Chemical Carbon Dioxide Sensors

Chemical carbon dioxide gas sensors consist of sensitive layers based on polymer- or heteropolysiloxane. They have very low energy consumption and can be reduced in size to fit into microelectronic-based systems.

Working Principle

The carbon dioxide gas sensor measures gaseous carbon dioxide levels by detecting the quantity of IR radiation absorbed by carbon dioxide molecules. The sensor employs a hot metal filament that acts as an IR source to generate IR radiation.

The IR source is located at one end of a sensor tube, and another end is provided with an IR sensor. The IR sensor measures the amount of radiation that passes through the sample without being absorbed by the carbon dioxide molecules.

The sensor measures the IR radiation absorbed in the narrow band at 4260 nm. The greater the absorbing gas concentration in the sampling tube, the lesser the amount of radiation from the source.

As a result of this increase in temperature, a voltage is generated, amplified and read by an interface system. Meanwhile, the carbon dioxide gas diffuses via the sensor tube by the eight vent holes.

Vernier Software and Technology provide a clear demonstration of how a modern-day carbon dioxide sensor works to measure the carbon dioxide concentration:

Vernier Carbon Dioxide Gas Sensor. Vernier Software & Technology, LLC.

Applications

Some of the major applications of carbon dioxide sensors include the following:

• It can be used for HVAC applications to monitor the quality of air.
• It is used to monitor fermentation, aerobic respiration, photosynthesis and other carbon dioxide consuming or producing processes.

References

• CO₂ Gas Sensor – Idaho State University
• Application of the Vernier CO₂ Gas Sensor – University of Central Arkansas

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