CO2 Measurement in Incubators - Questions and Answers - VAISALA - #1

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PRIMARY IMAGE AREA / APPLICATION NOTE INCUBATORS SEPTEMBER 2009 CO2 Measurement in Incubators - Questions and Answers The purpose of this document is to answer most frequently asked questions often proposed concerning CO2 measurement and products. 1. How does the CARBOCAP®, NDIR (non-dispersive infrared), single-beam, dual wavelength sensor work? The Vaisala CARBOCAP® Sensor has three major components: a light source, an interferometer, and an IR detector. The light source is positioned to shine at the IR detector so that the light travels a fixed distance to the detector, where the intensity of the light is measured. Frequently asked questions 1. How does the CARBOCAP®, NDIR (non-dispersive infrared), single beam, dual wavelength sensor work? 2. How do temperature and pressure affect CO2 measurement? 3. How can temperature and pressure error be corrected when using Vaisala CO2 products? 4. How can condensation be avoided when sampling from incubators? 5. Why is the CO2 concentration reading higher than expected when using the pump sampling method with drying tubing? Light source Volume occupied by gas Fabry Perot Interferometer IR Detector At the CO2 absorption wavelength, light is absorbed by the carbon dioxide present in the gas. The FPI tunes out of all other wavelengths, so the intensity of light reaching the IR Detector varies as a function of the amount of CO2 within the sensor. A Fabry-Perot Interferometer (FPI) is positioned just in front of the IR detector. The FPI is a tunable filter which allows only certain wavelengths of light to pass through to the detector. Carbon dioxide absorbs certain wavelengths of light and not others, so the FPI is designed to pass light at a CO2 absorption wavelength (4.26 ìm) and a nearby, non-absorbing wavelength. See the illustration on the left.