Teledyne 6750 - Total Organic Carbon analyzers - Manual (Page 29)

Total Organic Carbon Analyzer Theory of Operation
Teledyne Analytical Instruments 17
2.4.4 NDIR CO
2
Gas Detection
The key component for reliable TOC analysis is the precise and
interference-free detection of CO
2
. The Model 6750 NDIR unit requires
very little maintenance because of its ability to handle the corrosive
gases generated in TOC analysis. This is due in part to its non-reflective
borosilicate sample cell. It has no moving parts which further reduces
the maintenance load and it uses an internal self-calibrating technique.
The NDIR unit is shown in Figure 2-10. Some of the features of the
NDIR unit are as follows:
• Specific, interference-free CO
2
detection
• Dual-wavelength rationing compensates for drift
• Computer-controlled for accuracy
• Sapphire protected optics
• Non-corrosive, non-reflective sample cell (borosilicate)
• No moving parts or tools required for easy maintenance and
service
• No critical realignment required
Figure 2-10: Model 6750 NDIR Unit
The NDIR CO
2
detector uses a completely solid state, dual
wavelength ratioing technique with a single borosilicate sample cell that