The GMM 221 is part of Vaisala’s carbon dioxide line for Original Equipment Manufacturers (OEMs), utilizing Vaisala’s CARBOCAP® carbon dioxide sensor technology.
Figure 1: Vaisala GMM 221
As the GMM 221 is a carbon dioxide module, it relies on an internal sensor to take the measurements. The GMM 221 utilizes the Vaisala CARBOCAP® sensor, a silicon based non-dispersive infrared (NDIR) sensor. An infrared source at the end of the measurement chamber emits light into the gas chamber, where any CO2 present absorbs a part of the light at its characteristic wavelength. A measurement is also taken at a wavelength where no absorption occurs. The electronics of the instrument convert the ratio of the absorption measurements into a voltage output which indicates the CO2 reading.
The GMM 221 is a member of the GMM 220 Series of modules. The variations within the series consist of different measurement ranges for CO2 concentrations. The GMM 221 is designed for high CO2 concentration measurements, and can be calibrated to operate within one of five concentration ranges: 0-2%, 0-3%, 0-5%, 0-10%, and 0-20%. The GMM 222 is designed for low CO2 concentration measurements, and can be calibrated to operate within one of five concentration ranges: 0-2000 ppm, 0-3000 ppm, 0-5000 ppm, 0-7000 ppm, and 0-10000 ppm.
The GMM 221 can be integrated into equipment to work with the NI WSN in incubator applications. The probe features an IP65 classification housing.