TELEDYNE API T703U - The Measurement; Reference Cycle; Table 9-3: Photometer Measurement; Reference Cycle

Principles of Operation Teledyne API T703/T703U Calibrator Operation Manual
202
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inHg
LI
I
C
o
92.29
273
10
ln
9
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In a nutshell the photometer:
 Measures each of the above variables: ambient temperature; ambient gas
pressure; the intensity of the UV light beam with and without O
3
present;
 Inserts know values for the length of the absorption path and the absorption
coefficient, and:
 Calculates the concentration of O
3
present in the sample gas.
The Measurement / Reference Cycle 9.6.1.2.
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. A valve called the measure/reference valve, physically located on front-
left corner of the O
3
generator assembly (see Figures 3-4 and 9-14) alternates the
gas stream flowing to the photometer between zero air (diluent gas) and the O
3
output from the O
3
generator. This cycle takes about 6 seconds.
Table 9-3: Photometer Measurement / Reference Cycle
TIME INDEX
STATUS
0 sec.
Measure/Reference Valve Opens to the Measure Path.
0 – 2 sec.
Wait Period. Ensures that the Absorption tube has been adequately flushed of any
previously present gasses.
2 – 3 sec.
Analyzer measures the average UV light intensity of O
3
bearing Sample Gas (I) during
this period.
3 sec.
Measure/Reference Valve Opens to the Reference Path.
3 – 5 sec.
Wait Period. Ensures that the Absorption tube has been adequately flushed of O
3
bearing gas.
5 – 6 sec.
Analyzer measures the average UV light intensity of Non-O
3
bearing Sample Gas (I
0
)
during this period.
CYCLE REPEAT EVERY 6 SECONDS
07223D DCN7107