Teledyne GFC-7001T - Trace CO Analyzer - Manual (Page 289)

Theory of OperationTeledyne API – Model T300/T300M CO Analyzer
Teledyne Analytical Instruments
13. THEORY OF OPERATION
The GFC7001T/GFC7001TM Gas Filter Correlation Carbon monoxide Analyzer is a
microprocessor-controlled analyzer that determines the concentration of carbon
monoxide (CO) in a sample gas drawn through the instrument. It requires that the
sample and calibration gases be supplied at, or very close to, ambient atmospheric
pressure in order to establish a stable gas flow through the sample chamber where the
gases ability to absorb infrared radiation is measured.
Calibration of the instrument is performed in software and does not require physical
adjustments to the instrument. During calibration, the microprocessor measures the
current state of the IR Sensor output and various other physical parameters of the
instrument and stores them in memory.
The microprocessor uses these calibration values, the IR absorption measurements made
on the sample gas along with data regarding the current temperature and pressure of the
gas to calculate a final CO concentration.
This concentration value and the original information from which it was calculated are
stored in one of the unit’s internal data acquisition system (DAS - See Sections 7) as
well as reported to the user via front panel display display or a variety of digital and
analog signal outputs.
13.1. MEASUREMENT METHOD
This section presents measurement principles and fundamentals for this instrument.
13.1.1. BEER’S LAW
The basic principle by which the analyzer works is called the Beer-Lambert Law or
Beer’s Law. It defines how light of a specific wavelength is absorbed by a particular gas
molecule over a certain distance. The mathematical relationship between these three
parameters is:
I = I
o
e
-α Lc
Equation 13-1
Where:
I
o is the intensity of the light if there was no absorption.
I
is the intensity with absorption.