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142
Teledyne API – Model T400 O
3
Analyzer
083730400A DCN8130
6.1.3 T
HE
R
EFERENCE
/
M
EASUREMENT
C
YCLE
In order to solve the Beer-Lambert equation (see Section 6.1.1), 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 T400 accomplishes this by alternately sending the sample gas
directly to the absorption tube and passing it through a chemical scrubber that removes
any O
3
present.
Flow / Pressure
Sensor PCA
SAMPLE
PRESSURE
SENSOR
O
3
FLOW
SENSOR
Sample Gas
Flow Control
EXHAUST
GAS
OUTLET
Particulate
Filter
PUMP
DRY AIR
INLET
O
3
Scrubber
ABSORPTION TUBE
SAMPLE
GAS INLET
SPAN GAS
INLET
ZERO AIR
INLET
Measure/
Reference
Valve
Measure Path
Reference Path
Figure 6-2. Reference / Measurement Gas Cycle
The Measurement / Reference Cycle encompasses the following states and ~durations:
0 seconds Measure/Reference Valve Opens to the Measure Path.
0 – 2 seconds Wait Period. Ensures that the Absorption tube has been adequately
flushed of any previously present gasses.
2 – 3 seconds Analyzer measures the average UV light intensity of O
3
-bearing
Sample Gas (
I
) during this period.
3 seconds Measure/Reference Valve Opens to the Reference Path.
3 – 5 seconds Wait Period. Ensures that the Absorption tube has been adequately
flushed of O
3
bearing gas.
5 – 6 seconds Analyzer measures the average UV light intensity of non-O
3
-bearing
Sample Gas (
I
0
) during this period.
CYCLE REPEATs EVERY 6 SECONDS
Содержание T400
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