Teledyne 400E, Instruction Manual, Page: 219 / 318

Model 400E Ozone Analyzer
Instruction Manual THEORY OF OPERATION
P/N 04316 Rev: B 219
In order to account for this effect the following addition is made to the equation:






×
Κ
×




×






=
?
?
L I
I
C
o
o
inHg 92 . 29
273
1
ln
α
Where:
T
= sample temperature in Kelvin
P
= sample pressure in inches of mercury
Finally, to convert the result into Parts per Billion (PPB), the following change is
made:






Ρ
×
Κ
Τ
×






×






=
−
inHg
L I
I
C
o
o
92 . 29
273
10
ln
9
α
In a nutshell the Model 400E Ozone Analyzer:
Measures each of the above variables: Sample Temperature; Sample
Pressure; the Intensity of the UV light beam with and without O
3
present,
Inserts known values for the Length of the Absorption Path and the Absorption
Coefficient, and
Calculates the concentration of O
3
present in the sample gas.
10.1.2.
The Absorption Path
In the most basic terms, the Model 400E uses a high energy, mercury vapor lamp
to generate a beam of UV light. This beam passes through a window of material
specifically chosen to be both non-reactive to O
3
and transparent to UV radiation at
254nm and into an absorption tube filled with Sample Gas.
Because ozone is a very efficient absorber of UV radiation the Absorption Path
Length required to create a measurable decrease in UV intensity is short enough
(approximately 42 cm) that the light beam is only required to make pass through
the Absorption Tube. Therefore no complex mirror system is needed to lengthen the
effective path by bouncing the beam back and forth.