Measurement principle

Fluorescent indicator

The reaction of CO2 with the sensing film indicator begins about a change in its color and/or luminescent properties. For the fluorescence-based film this change entails a shift in the excitation spectrum to a shorter wavelength. The reaction of CO2 with the indicator is fully reversible so that CO2 is released from the indicator following a drop in CO2 levels with the indicator reverting to its initial longer wavelength excitation form. As with Polestar’s pH sensing chemistry, the degree of indicator shift from bound CO2 to CO2 free can be determined using a ratio of fluorescence emission signals acquired under two different wavelengths of excitation or the reflected optical signal at two different wavelength regions in the case of the colorimetric-based sensing film.

 

Available ranges of operation

Colorimetric CO2 – 0 to 25 mbar
Fluorescent CO2 – 0 to 80% (1 ATM)