Vaisala CARBOCAP® technology for demanding environments

First launched in 1997, the Vaisala CARBOCAP® sensor features a groundbreaking innovation – the micromachined, electrically tunable Fabry-Pérot Interferometer (FPI) filter for built-in reference measurement. This reliable and stable sensor has been delivering accurate 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

Gases have a characteristic absorbance band in the infrared (IR) region, each at a unique wavelenght. When IR radiation is passed through a gas containing another gas we are measuring, part of the radiation is absorbed. Therefore, the amount of radiation passing through the gas depends on the amount of the measured gas present, and this can be detected with an IR detector.

The Vaisala CARBOCAP® sensor features an electrically tunable FPI filter. In addition to measuring gas 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 non-absorption 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 several absorption and reference wavelengths with a single light source are known as single-beam multi-wavelenght instruments.The technology is widely applied in costly analyzers. The unique feature of the CARBOCAP® sensor is its micromachined FPI filter, which performs a multiwavelength 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® sensor technology is well suited to a wide range of applications, but since the final customer value for each industrial application is unique, it depends on the product line how the CARBOCAP® sensor technology is implemented. In carbon dioxide measurement products, the technology is utilized for both ppm (parts per million) and percentage level 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 incubators.

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 such as biogas process lines, where excellent long-term stability and tolerance to harsh conditions are important requirements. For biogas applications, the technology is applied for multigas measurements, as it also helps improve the methane quality in the process.

Product examples

Vaisala's instruments including the CARBOCAP® sensor technology range from hand-held meters, measurement modules, and industrial transmitters for CO₂ measurements to multigas
measurement solutions.