Model 400E Ozone Analyzer
Instruction Manual
EPA Protocol Calibration
P/N 04316 Rev: B
195
When F
d
has been adjusted and R has been calculated, assay the diluted
concentration with the photometer and then compare the diluted assay (A
2
) with
the original undiluted assay (A
1
) by calculating the percentage of linearity error (E)
according to the following equation.
E
A
A
R
A
=
−
×
1
2
1
100
(
/
)
This linearity error must be <5% in magnitude and should be <3% for a well-
performing system.
NOTE
The result is not the true linearity error because it includes possible
instrument errors in the flow measurements. This test technique
should only anbe used as an indicator.
If the linearity error is >5% or is greater than you expect it to be, check and verify
the accuracy of the flow dilut ion carefully before assuming that the photometer is
inaccurate. The test should be carried out several times at various dilution ratios,
and an averaging technique should be used to determine the final result.
If the linearity error is excessive and cannot be attributed to flow measurement
inaccuracy, check the photometer system for:
1.
Dirty or contaminated cell, lines, or manifold.
2.
Inadequate "conditioning" of the system.
3.
Leaking of two-way valve or other system components.
4.
Contaminated zero-air.
5.
Non-linear detectors in the photometer.
6.
Faulty electronics in the photometer.
8.4.2.
O
3
Loss Correction Factor
In spite of scrupulous cleaning and preconditioning, some O
3
may be lost on contact
with the photometer cell walls and the gas-handling components. Any significant
loss of O
3
must be quantitatively determined and used to correct the output
concentration assay. In any case, the O
3
loss must not exceed 5%.