CO2 Measurement in Incubators - Questions and Answers0 pages

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.