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Linearity Check
Thermo Scientific
11. Replace access fittings used in steps 8 and 10, and make sure they are
leak tight.
12. Compute percent of ozone loss from the following equation:
Percent of Ozone Loss =
R
1/4[R(a)
m
If the ozone loss is greater than 2%, check that the absorption cells and
PTFE tubing have not become contaminated by dirt. See
Cleaning" in the "Maintenance" chapter for more information. If the cells
and PTFE tubing are clean, recondition the optical bench by setting the
ozone generator for maximum ozone and adjust the pressure regulator for
minimum dump flow (about 1/2 liter per minute). Let the calibration
photometer run overnight sampling the high level of ozone. Then repeat
ozone loss test.
Since the 49iQ is inherently linear over the range of interest (0-1 ppm), a
linearity test is an effective overall test that the instrument is operating
properly. The checks above should identify whether any causes of non-
linearity are present. The possible causes of non-linearity are:
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:
R(a)
R(b)
input
out
input
R
m
Calibration
Calibration Photometer System Preparation
R(b)
]
out
100
%
"Optical Bench
49iQ Instruction Manual
4-5
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