Servomex SERVOTOUGH Oxy, Руководство оператора

Страница: 133 / 145

01910001B_8 © Servomex Group Limited. 2020
121
Appendix D PARAMAGNETIC CORRECTION FACTORS
For
a paramagne�c oxygen measurement, the composi�on of any typical background gas in the gas
sample 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.
Background gas
E r ror
Background gas
E r ror
Hydrogen 0.26%
Methane -
0.18%
Carbon dioxide -
0.30%
Propane -
0.87%
Note:
The correction is directly proportional to the concentration of the background gas in
the sample being measured, and in many cases can be ignored.
Note:
All corrections must be calculated using 60°C data from the tables below.
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.
Note:
Example: If you are measuring 10% Oxygen in a background of 70% Hydrogen and
20% Carbon Dioxide the correction factor would be:
The correction factor assumes 100% of background gas, so you must firstly correct for
the nominal process oxygen concentration:
Total background concentration = 70% + 20% = 90%
Correct background concentrations for 0% oxygen:
(100% / 90%) x 70% = 77.8% Hydrogen
(100% / 90%) x 20% = 22.2% Carbon Dioxide
For 100% Hydrogen the correction is 0.26, so for 77.8% it is 0.202
For 100% Carbon Dioxide the correction is
-
0.30, so for 22.2% it is
-
0.067
So
the total correction factor in this case is
-
0.067 + 0.202 = 0.135