How can temperature and pressure errors be corrected when using Vaisala CO2 products?

Carbon dioxide measurements made at temperatures and pressures different from the calibration conditions need to be corrected. The required compensation for any NDIR sensor is based on the ideal gas law. The simplest form of correction for a volume percent reading can be done using a formula according to the ideal gas law:

On some of the instruments (GM70, GMT220, GMM220 and GMP343) an internal correction can be applied.  The internal correction is a more accurate way to make compensations because in addition to taking into account the ideal gas law, it takes into account dependencies caused by real gas laws, as well as the electronics and optical components of the instrument.

For instructions on how to set the temperature and pressure on these transmitters, please refer to the user guides.