Teledyne gfc 7000ta operation manual Teledyne Analytical Instruments 192

Theory of Operation Model GFC7000TA Carbon Dioxide Analyzer

9.1.4.1. Ambient CO2 Interference Rejection

CO2 absorbs IR light very well. So well that even the narrow volume of ambient air between the IR source and the sample chamber is enough to alter the analyzer’s measured concentration of CO2. Also, ambient air, which averages around 350 ppm to 400 ppm, will vary significantly over the course of the day. The ambient CO2 concentration can rise as high as 1 000 ppm during the time of the day when people are present. It can fluctuate ± 300 ppm as the photosynthesis of plant life in the nearby area increases during the day and decreases at night.

The basic design of the GFC 7000TA rejects most of this interference at a 100:1 ratio; however this still can allow small fluctuations in CO2 concentration during the course of the day. To completely remove all effects of ambient CO2 from the analyzer’s measurement of CO2, dried air, scrubbed of all CO2 is pumped into the GFC wheel housing to purge all ambient CO2 (see Figure 10-7)

Teledyne Analytical Instruments 192