Vaisala CARBOCAP® Technology First launched in 1997, the Vaisala CARBOCAP® carbon dioxide (CO2) sensor features a groundbreaking innovation – the micromachined, electrically tunable Fabry-Perot Interferometer (FPI) filter for built-in reference measurement. This reliable and stable sensor has been delivering accurate CO2 measurements since the late 1990s across a wide range of industries and applications, from building automation and safety to life sciences and ecological research. How It Works Carbon dioxide has a characteristic absorbance band in the infrared (IR) region at a wavelength of 4.26 μm. This means that when IR radiation is passed through a gas containing CO2, part of the radiation is absorbed. Therefore, the amount of radiation passing through the gas depends on the amount of CO2 present, and this can be detected with an IR detector. The Vaisala CARBOCAP® sensor features an electrically tunable FPI filter. In addition to measuring CO2 absorption, the micromechanical FPI filter enables a reference measurement at a wavelength where no absorption occurs. When taking the reference measurement, the FPI filter is electrically adjusted to switch the bypass band from the absorption wavelength to a nonabsorption wavelength. The reference measurement compensates for any potential changes in the light source intensity, as well as for contamination and dirt accumulation in the optical path. This feature means that CARBOCAP® sensor operation is highly stable over time. Instruments measuring at both the absorption and the reference wavelength with a single light source are known as single-beam dual-wavelength instruments. The technology is widely applied in costly analyzers. The unique feature of the CARBOCAP® sensor is its micromachined FPI filter, which performs a dual-wavelength measurement using a single detector. The compact size of the sensor means that this advanced technology can be incorporated into small probes, modules, and transmitters. Typical Applications for Carbon Dioxide Measurement Vaisala CARBOCAP® instruments are well suited to a wide range of applications, from ppm (parts per million) to percentage-level CO2 measurements. Since CO2 replaces oxygen, it can be harmful to people in very high concentrations. CO2 is present at percentage levels only within closed processes such as fermentation and controlled-atmosphere storage environments. Percentage-level measurements are also typical in life-science applications such as CO2 incubation. Normal atmospheric air includes CO2 at ppm levels. Typical CARBOCAP® applications include ventilation control in buildings occupied by people, animal shelters, and greenhouses. In areas where large volumes of CO2 are handled, reliable CO2 measurement with alarm control is an important safety precaution.The CARBOCAP® sensor is also a popular choice in ecological measurement applications, where excellent long-term stability and tolerance to harsh conditions are important requirements. CARBOCAP® CO2 Products Vaisala offers instruments for measuring CO2 at ppm and percentage levels in both indoor and outdoor environments. Vaisala's wide variety of CO2 instruments ranges from hand-held meters, measurement modules, and industrial transmitters to high-volume, affordable transmitters for volume applications. Typical CARBOCAP® applications include ventilation control in animal shelters.