Teledyne T360 Manuel d'utilisateur télécharger pdf (Page 196)

Principles of Operation Teledyne API Model T360/T360M Operation Manual

194

7.1.2. Measurement Fundamentals

In the most basic terms, the Model T360 uses a high energy heated element to

generate a beam of broad-band IR light with a known intensity (measured during

Instrument calibration. This beam is directed through multi-pass cell filled with

sample gas. The sample cell uses mirrors at each end to reflect the IR beam back

and forth through the sample gas to generate a 2.5 meter absorption path (see

Figure 7-1). This length was chosen to give the anal

zer maximum sensitivity to

fluctuations in CO

density.

Source

IR Beam

Sample Chamber

Band-Pass Filter

Photo-Detector

Figure 7-1: Measurement Fundamentals

Upon exiting the sample cell, the beam shines through a band-pass filter that

allows only light at a wavelength of 4.3 µm 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.

7.1.3. Gas Filter Correlation

Unfortunately, water vapor absorbs light at 4.3 µm too. To overcome the

interfering effects of water vapor the Model T360 adds another component to the

IR light path called a gas filter correlation (GFC) wheel (see Figure 7-2).

Measurement Cell

(Pure N

)

Reference Cell

with CO

)

Figure 7-2: GFC Wheel

07272B DCN6552

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Teledyne T360 Manuel d'utilisateur Page 196