The Reference / Measurement Cycle; Figure 10-1: O; Figure 10-2: Reference / Measurement Gas Cycle - Teledyne 400E Instruction Manual

THEORY OF OPERATION
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
tube.
Window
UV
Source

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
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
From Sample
Port
To Exhaust
Port
220
ABSORPTION TUBE
Sample Gas IN
Absorption Path Length = 42 cm

Figure 10-1: O

Measure Path
Particulate
Filter
PUMP

Figure 10-2: Reference / Measurement Gas Cycle

Sample Gas OUT
Absorption Path
3
present.
3
Reference Path
O
3 Path
Scrubber
ABSORPTION TUBE
Model 400E Ozone Analyzer
Instruction Manual
in the absorption
3
Window
UV Detector
Reference/
Measure
Valve
Valve switches
every 3 seconds
P/N 04316 Rev: B
is
3