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TELEDYNE INSTRUMENTS
460L Instruction Manual Theory of Operation
05228 Rev B 53
DCN 5164 PRINTED DOCUMENTS ARE UNCONTROLLED
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.
Finally, the UV then passes through a 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 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 = 16 cm
Figure 10-1 O
3
Absorption Path
10.1.3. The Reference / Measurement Cycle
In order to solve the Beer-Lambert equation 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 460L
accomplishes this by alternately passing the sample gas through a chemical scrubber that
removes any O
3
present and sending it directly to the absorption tube.
ABSORPTION TUBE
Particulate
Filter
From Sample
Port
PUMP
O
3
Scrubber
Reference/
Measure
Valve
To Exhaust
Port
Valve switches
every 3 seconds
Measure Path
(I)
Reference Path
(I
0
)
Figure 10-2 Reference / Measurement Gas Cycle