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TELEDYNE API
Theory of Operation M703E Calibrator Operator’s Manual
In order to account for this effect the following addition is made to the equation:
Equation 9-7
×××=
Ρ
inHg92.29
Κ273
Τ
Lα
1
I
I
lnC
o
o
Where:
T = sample ambient temperature in degrees Kelvin
P = ambient pressure in inches of mercury
Finally, to convert the result into Parts per Billion (PPB), the following change is made:
Equation 9-8
×××=
Ρ
inHg92.29
Κ273
Τ
Lα
10
I
I
lnC
o
9
o
In a nutshell the M703E 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.
9.6.1.2. The Measurement / Reference 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. 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 9-4: M703E 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 Seconds
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 Seconds
Analyzer measures the average UV light intensity of Non-O
3
bearing Sample Gas (I
0
)
during this period
.
CYCLE REPEAT EVERY 6 SECONDS
156 05744 Rev B