Servomex SERVOTOUGH Oxy, Operator'S Manual

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60
© Servomex Group Limited. 2020 01910001B_8
Figure
57 -
mA Range Indica�on
5.18
Correcting O
2
measurements for background gases
Note:
If you are measuring O
2
(oxygen) in a background of nitrogen or air, you do not need
to correct the measurements.
5.18.1
Overview of measurement errors
For
a paramagne�c oxygen measurement, the composi�on of any typical background gas in the gas
sa
mple will have a minor effect on the analyser
measurement. For an
analyser which has been ’Lo’
calibrated with N2 (nitrogen) and ’Hi’ calibrated with O
2
, some examples of cross
-
interference errors
(that is, O
2
measurement errors) in gases
which contain 100% of a background gas are shown below. See
Appendix D
for more correc�ons.
Background gas
E r ror B ac
kground gas
E r ror
Hydrogen 0.26%
Methane -
0.18%
Carbon dioxide -
0.30%
Propane -
0.87%
Note:
The error is directly proportional to the concentration of the background gas in the
sample being measured, and in many cases can be ignored.
Note: All corr
ections must be calculated using 60
°C
data from the tables in Appendix D.
If you cannot ignore the error, you can use the procedure in Sec�on 5.18.2 to enter a compensa�on to
correct for the error. Example correc�ons are shown below.
Note:
Example:
If you are measuring O
2
(oxygen) in a background of Carbon dioxide
-
0.30 should be
entered as the cross interference offset.