Teledyne M300EM operation manual Gas Filter Correlation, 1:Measurement Fundamentals, 2:GFC Wheel

Theory of Operation Teledyne API – Technical Manual - Model 300E Family CO Analyzers

Lengthening the absorption path is accomplished partly by making the physical dimension of the reaction cell longer, but primarily by adding extra passes back and forth along the length of the chamber.

Table 11-1: Absorption Path Lengths for M300E and M300EM

MODEL	TOTAL NUMBER OF	DISTANCE BETWEEN MIRRORS	TOTAL
			ABSORPTION LIGHT
	REFLECTIVE PASSES
			PATH
M300E	32	437.5 mm	14 Meters
M300EM	8	312.5 mm	2.5 Meters

IR

Source

Band-Pass Filter

Sample Chamber

Photo-Detector

IR Beam

Figure 11-1: Measurement Fundamentals

Upon exiting the sample cell, the beam shines through a band-pass filter that allows only light at a wavelength of

4.7µm to pass. Finally, the beam strikes a solid-state photo-detector that converts the light signal into a modulated voltage signal representing the attenuated intensity of the beam.

11.2.1.GAS FILTER CORRELATION

Unfortunately, water vapor absorbs light at 4.7 µm too. To overcome the interfering effects of water vapor the M300E/EM adds another component to the IR light path called a Gas Filter Correlation (GFC) Wheel.

Measurement Cell

(Pure N2)

Reference Cell

(N2 with CO)

Figure 11-2: GFC Wheel

230 04288D DCN5752