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CO2 Sensor Response Time

Pyreos infrared detectors are particularly well suited for gas detection with the NDIR spectroscopy method

NDIR spectroscopy is based on a simple yet effective principle of absorption of a wide spectral source by a chosen gas and monitoring detector signal changes at a particular detection wavelength, which correlate to the gas absorption characteristics. IR emitter (usually a bulb or a MEMS based device) is used to fill the gas tube with a broad range of wavelengths corresponding to the blackbody radiation. Some of these wavelengths will become absorbed by the gas, e.g. CO2 absorbs well around ~4.26 μm. If such broad spectrum interacted directly with a detector, it would not be possible to measure changes at the gas absorption band. A narrowband filter is required to block everything but the gas absorption band. For example 4.26/90 (CWL/FWHM) in case of CO2.

Non-standard filters

Certain NDIR spectroscopy applications require filters which are not typical for most common applications and must poses bespoke spectral characteristics. Reasons for a new type of filter are usually:
▪ detection of a novel type of gas or gas mixtures (e.g. a new refrigerant),
▪ spectral variations in the gas detection module
▪ spectral shift to a non-saturated region
Pyreos works with a network of qualified filter suppliers. Pyreos is able to provide infrared detectors with the appropriate narrowband filter to suit a customer’s requirement. A standard and off-the-shelf list of such filters can be found on some of our datasheets or on the Pyreos website: https://pyreos.com/infrared-sensing-by-wavelength/
Bespoke filter wavelengths and bandwidths are available upon request