Thermo Scientific 49i Instruction Manual page 142

Calibration
Calibration Photometer System Preparation
4-6 Model 49i Instruction Manual
• Dirty or contaminated cell, lines, or manifold
• Inadequate conditioning of system
• Leaks in system
• Contamination in zero air
• Non-linear detectors in photometer
• Faulty electronics
To demonstrate linearity, generate a concentration of ozone near the upper
range limit of the calibration photometer and accurately dilute the ozonated
air with zero air. To do this test accurately, two calibrated flow meters and a
mixing chamber are needed: one flow meter to measure the flow into the
ozonator, and the other to measure the flow of the dilutant zero air. The
percent of non-linearity is calculated as follows:
F
o
R
F F
o d
A
2
A
1
R
E 100%
A
1
where:
F = Ozonator flow
o
F = Dilutant zero air flow
d
E = Linearity error, in percent
A = Assay of original concentration
1
A = Assay of diluted concentration
2
R = Dilution ratio
Note that the inherent linearity accuracy of the Model 49i Primary Standard
(or modified Model 49i) is greater than the accuracy measurements of the
mass flow meters.
(2)
(3)
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