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Altech Environmental

CO2 - Carbon Dioxide Monitoring and Analysis


Altech offers CO2 CEMS or CO discrete analyzers for the continuous measurement of carbon dioxide. Carbon dioxide is measured using either NDIR or FTIR technologies.

In Altech’s flagship MIR 9000, MIR 9000 CLD, MIR-IS and MIR 9000H analyzers, non-dispersive infrared technology (NDIR) using the Gas Filter Correlation (GFC) technique is used to measure CO2. The infrared bench consists of a light source, chopper, multipass sample cell, filter wheels, and solid-state detector. The filter wheel containing the optical filter and gas cells provides a dual function. One is to modulate the light; the second is to isolate the wavelengths for measurement. This configuration provides for a much simpler optical and mechanical system. The modulated light is sent into a temperature stabilized (50ºC) multipass sample cell. The MIR 9000 is available in cold/dry and hot/wet configurations.

FTIR is the other method of analysis used for CO2 measurements. Unlike dispersive instruments, which look at a specific wavelength, the FTIR device scans the entire spectrum using a device called an interferometer. The interferometer produces a unique type of signal which has all of the infrared frequencies “encoded” into it. The signal can be measured very quickly, usually on the order of one second or so. Thus, the time element per sample is reduced to a matter of a few seconds rather than 20-120 seconds. Most interferometers employ a beamsplitter which takes the incoming infrared beam and divides it into two optical beams. One beam reflects off of a flat mirror which is fixed in place. The other beam reflects off of a flat mirror which is on a mechanism which allows this mirror to move a very short distance (typically a few millimeters) away from the beamsplitter. The two beams reflect off of their respective mirrors and are recombined when they meet back at the beamsplitter. Because the path that one beam travels is a fixed length and the other is constantly changing as its mirror moves, the signal which exits the interferometer is the result of these two beams “interfering” with each other. The resulting signal is called an interferogram which has the unique property that every data point (a function of the moving mirror position) which makes up the signal has information about every infrared frequency which comes from the source. Since the measured interferogram signal cannot be interpreted directly as gas concentrations, a means of “decoding” the individual frequencies is required. This is accomplished via the well-known mathematical technique called the Fourier Transformation. This transformation is performed by the computer which then presents the user with the desired spectral information for analysis.

Contact Altech for any questions you may have related to CO2 CEMS, discrete CO2 analyzers, NDIR or FTIR technologies at 630.262.4400 or sales@altechusa.com.

Since we offer all common CO2 measurement technologies and analyzer manufactures (if you require a specific manufacturer or model), Altech tailors its system offering to your specific application. Altech’s instruments that measure CO2 are as follows:

Emission Monitoring

Air Quality Monitoring

Engine Gas Monitoring