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THEORY OF OPERATION
Model 400E Ozone Analyzer
Instruction Manual
220
P/N 04316 Rev: B
Finally, the UV then passes through similar window at the other end of the
Absorption Tube and is detected by a specially designed vacuum diode that only
detects radiation at or very near a wavelength of 254nm. The specificity of the
detector is high enough that no extra optical filtering of the UV light is needed.
The detector assembly reacts to the UV light and outputs a voltage that varies in
direct relationship with the light’s intensity. This voltage is digitized and sent to the
instrument’s CPU to be used in computing the concentration of O
3
in the absorption
tube.
UV
Source
ABSORPTION TUBE
UV Detector
Sample Gas IN
Sample Gas OUT
Window
Window
Absorption Path Length = 42 cm
Figure 10-1: O
3
Absorption Path
10.1.3.
The Reference / Measurement Cycle
In order to solve the Beer-Lambert equation (see Section 10.1.2) it is necessary to
know the intensity of the light passing through the Absorption Path both when O
3
is
present and when it is not. The Model 400E accomplishes this be alternately
sending the Sample Gas directly to the Absorption tube and passing it through a
chemical Scrubber that removes any O
3
present.
ABSORPTION TUBE
Particulate
Filter
From Sample
Port
PUMP
O
3
Scrubber
Reference/
Measure
Valve
To Exhaust
Port
Valve switches
every 3 seconds
Measure Path
Reference Path
Path
Figure 10-2: Reference / Measurement Gas Cycle
Содержание 400E
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