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Knowledgebase >

Infrared carbon dioxide sensors

3 Mins

Knowledgebase >

Infrared carbon dioxide sensors

Our carbon dioxide analyzers use infrared technology to measure percentage levels of the gas in most industrial processes. 

 

Infrared carbon dioxide sensors

 

Designed by Systech Illinois, our global manufacturer of moisture, gas and oxygen analyzers, this innovative testing instrument uses an infrared sensor to capture accurate CO2 measurements. 

 

Our infrared carbon dioxide sensors are fitted with a self contained unit, mounted inside the gas analyzer, which sends the data electronically through to an easy-to-read digital display. 

 

The theory behind carbon dioxide gas detection

 

A given light source emits light across a wide range of wavelengths. Only a narrow band is visible (400-800nm) to the human eye. Wavelengths longer than 800nm are classed as infrared wavelengths’. Wavelengths that are shorter than 400nm are labelled in the ultraviolet region of the spectrum.

Figure 1. Spectrum from a light source

When a light source is exposed to a gas stream containing carbon dioxide, energy from the infrared region of the spectrum is absorbed by the gas. This energy affects the physical nature of the carbon dioxide molecule.

A carbon dioxide molecule consists of one carbon atom and two oxygen atoms. Both of the oxygen atoms are chemically attached to the carbon atom by double bonds as shown here.

Figure 2. Carbon dioxide molecule

When this molecule absorbs energy, the atoms interact with each other. The absorbed energy makes the atoms vibrate and rotate. The vibrational and rotational energy required from the light source is wavelength specific. Because the carbon to oxygen double bond is so prevalent in carbon dioxide, we can focus on the wavelength that causes the vibrational interaction.

Figure 3. Vibrational interaction between carbon and oxygen molecules.

The graphic above shows the interaction between the carbon and oxygen molecules when infrared light is absorbed. The carbon atom vibrates between the two oxygen atoms.  The amount of light absorbed by the gas stream is directly proportional to the carbon dioxide content in the gas stream.

Principle of operation

Two optical filters are mounted on the detector surface. One filter is chosen to pass the infrared light specific to carbon dioxide (measurement filter). The second filter is a reference filter. Light at a wavelength, that is not absorbed by carbon dioxide, passes through the reference filter. The difference in the amount of light between the two filters provides the amount of energy (light) absorbed by carbon dioxide. Clever stuff right?

 

The signal generated by the sensor is non-linear. It is fed to the electronics where it is linearized. Then a digital measurement of carbon dioxide concentration is displayed.

Principle of carbon dioxide detection

Two optical filters are mounted on the detector surface. One filter is chosen to pass the infrared light specific to carbon dioxide (measurement filter). The second filter is a reference filter. Light at a wavelength, that is not absorbed by carbon dioxide, passes through the reference filter. The difference in the amount of light between the two filters provides the amount of energy (light) absorbed by carbon dioxide. Clever stuff right?

 

The signal generated by the sensor is non-linear. It is fed to the electronics where it is linearized. Then a digital measurement of carbon dioxide concentration is displayed.

Calibration of infrared carbon dioxide sensors

The sensor requires a two-point calibration. First, the carbon dioxide sensor must be zeroed. This is performed by flowing a gas, without carbon dioxide, through the analyzer and adjusting the zero on the analyzer.

 

Second, the span needs to be adjusted. A span gas containing an amount of carbon dioxide – close to the concentration of carbon dioxide found in the sample gas – should be used to span the analyzer. The span gas should be of a known concentration and is typically available from a gas supplier.

 

With span gas flowing through the infrared carbon dioxide analyzer, the span should be adjusted to match the certified value.

Applications of infrared carbon dioxide sensors

The infrared analyzers may be used for measurement of carbon dioxide at any level between 0-100% in gases or gas mixtures.

 

The gaspace advance, gaspace advance micro and portamap gas analyzers are used by industrial gas producers, industrial gas users, and for safety monitoring

ApplicationUses
Gas ProducersOur customers use our testing devices to ensure the quality of their products, by measuring for carbon dioxide impurity, or they use them to monitor carbon dioxide purity.
Gas UsersOur customers use our testing instruments to check the modified atmosphere in food packaging, ensuring the quality of the gases used as production materials in the chemical industry

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