Model 202 Ozone Monitor Manual Rev. J-4
23
6.5.1. Setup Check
A visual inspection of the calibration setup should be performed before calibration to
verify that the setup is in proper order. All plumbing connections should be checked
and verified to follow the manufacturer's instructions. Any obvious leaks should be
fixed and the manifold and sampling lines should be checked for general cleanliness.
For more information, refer to the manufacturer's User Manual for the primary ozone
standard or ozone transfer standard.
6.5.2. Ozone Loss Test
Some ozone may be lost in the calibration setup due to reaction with the walls of the
manifold and sampling lines. Any significant loss of ozone must be measured and be
subsequently applied to correct the calibration measurements. For more information,
refer to the manufacturer's User Manual for the primary ozone standard or ozone
transfer standard.
6.5.3. Linearity Check
Since the Model 202 is inherently linear over several orders of magnitude, a linearity
check provides a test that the instrument is operating properly. Instrument linearity
can be checked by comparison to an ozone standard (see Calibration Procedure
–
Calibration Curve) or by dilution of an ozone measurement. To check the instrument
linearity by dilution of an ozone measurement, generate and measure a concentration
of ozone near the upper range of ozone monitor (80% of full scale is recommended).
Additional ozone concentrations should be generated by accurately diluting the ozone
flow with zero air and each concentration should be measured once the instrument
reaches a stable response. The accuracy of the linearity test relies on the accuracy of
the flow meters used to perform the dilution. The percent of non-linearity is calculated
from the formula:
d
o
o
F
F
F
R
+
=
(2)
%
100
1
2
1
x
C
R
C
C
E
+
=
(3)
where:
R = Dilution ratio
F
o
= Ozone generator flow
F
d
= Diluent zero air flow
E = Linearity error, in percent
C
1
= Measured concentration of original concentration
C
2
= Measured concentration of diluted concentration
The linearity error should not be greater than 5%. If the error is greater than 5%, the
accuracy of the flow dilution should be checked before assuming that the ozone
monitor is not linear. Note that the inherent linearity of the Model 202 is better than
the error calculated in this linearity check due to the uncertainty introduced by the flow
measurements.
