Thermo Electron 48C, Instruction Manual

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Chapter 1 Introduction
The CO gas filter acts to produce a reference beam which cannot be further attenuated by
CO in the sample cell. The N
2
side of the filter wheel is transparent to the infrared
radiation and therefore produces a measure beam which can be absorbed by CO in the
cell. The chopped detector signal is modulated by the alternation between the two gas
filters with an amplitude related to the concentration of CO in the sample cell. Other
gases do not cause modulation of the detector signal since they absorb the reference and
measure beams equally. Thus the GFC system responds specifically to CO.
The Model 48C outputs the CO concentration to the front panel display and the analog
outputs.
Figure 1-1 . Model 48C Flow Schematic
B42P809
1-2