Teledyne IR-7000 - Non-dispersive infrared series - Manual (Page 16)

Operational Theory
2.1 Introduction
The IR7000 is a microprocessor controlled, single beam infrared
analyzer that employs an electronically modulated IR source with no
moving parts.
The analyzer is composed of 2 subsystems:
• Optical Bench
• Electronics
2.2 Optical Bench
At the heart of the IR7000 NDIR Gas Analyzer is the patented dual
chambered balanced detector. The advanced detector design offers higher
sensitivity and selectivity with a greater dynamic range compared to other
IR detectors in the marketplace.
The optical bench is shown in Figure 2-1. It consists of:
• Sample cell
• Detector
• IR source
• Filter cell
• Windows and seals
The sample cell is a gold coated glass tube (metal Tube Optional)
through which the sample gas flows. At one end of the sample cell,
infrared energy is generated by a modulated IR source. The modulation is
achieved electronically by feeding the IR source a 4 Hz square wave
generated by the source control circuit on the main PC board. The
electronic modulation is very stable and eliminates the need for
mechanical choppers and motors routinely used in other IR systems. At
the other end of the optical bench is the detector and filter cell.