Teledyne 514 - NDIR analyzer - Manual (Page 5)

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Introduction 1.0
Teledyne Analytical Instruments
A Business Unit of Teledyne Electronic Technologies
1.0 Introduction
The Model 514 Photometric Analyzer measures the concentration of
one component in a mixture of liquids or gases continuously by measuring
the radiation absorbed in selected bands in the near infrared (NIR) spectral
region. Most liquids or gases having a characteristic absorption spectrum in
this region can be measured with the analyzer. When we refer to the NIR
region we mean that portion of the electromagnetic energy spectrum from
1.0 to 2.8
µ . This range can be extended to somewhat longer wavelengths
using special detectors. Most organic and some inorganic compounds can be
analyzed in the NIR region.
For example, the 514 is used to analyze parts per million (PPM) or the
percentage concentration of water in a variety of compounds (see Typical
Applications). The analyzer can also be used to measure the concentration of
one organic compound in the presence of another organic compound.
1.1 Method of Analysis
The 514 contains an optical system consisting of a quartz iodine source
lamp for NIR energy emission, collimating lens, sample cell and detector.
Isolator or light beam tubes filled with nitrogen gas interconnect the source
and sample, and sample and detector modules. In front of the detector is a
motor-driven filter wheel containing two optical interference-type filters,
located 180° from each other. These filters, designated the reference and
measuring filters, are alternately and continuously rotated in and out of the
optical path. The sample flows continuously through the sample cell absorb-
ing energy at various wavelengths throughout the NIR spectrum. The wave-
lengths and intensities of absorption peaks throughout the spectrum are
characteristic of the specific compounds that are present in the sample.
In any photometric analysis, there is always the component that we are
interested in analyzing, and background components that we are not inter-
ested in measuring. Both the component of interest and the background
component may have complex NIR absorption spectra.