91518 Multigas Analyzer Service Manual
3-7
Theory
Figure 3-4: Gas tubing layout
Gas Measuring Unit
The gas measuring unit is a nondispersive infrared analyzer, measuring absorption of the gas sample (CO
2
,
N
2
O, halothane, enflurane, isoflurane, desflurane, and sevoflurane) at seven infrared wavelengths, which are
selected using optical narrow band filters. The infrared radiation detectors are thermopiles.
Figure 3-5: Gas analyzer in principle
Concentrations of CO
2
and N
2
O are calculated from absorption measured at 3 to 5 µm (refer to
