MultiExact Gas Analyser
5 – Installation and set-up
5.8
Configuring and using the voltage outputs (option)
5.8.1 Overview
The analyser can be supplied with a voltage output for each sample gas measurement
for which the analyser is configured. The output is set up in the same way as for mA,
however:
•
The voltage range is 0 to 10 V
•
There is no 'underrange' facility
•
The jam 'High' output value will be held at 10.75 V
•
The jam 'Low' output value is held at 0 V
5.9
Correcting O
2
measurements for background gases (purity or control only)
☞
If you are measuring O
2
(oxygen) in a background of nitrogen or air, you do not
need to correct the measurements.
5.9.1 Overview of measurement errors
For an O
2
purity or control transducer, the composition of any typical background gas
in the gas sample will have a minor effect on the analyser measurement. The following
table gives 4 examples of cross-interference errors (O
2
measurement errors) in gases
which contain 100% of a specific background gas, for an analyser which has been 'Lo'
calibrated with N
2
(nitrogen) and 'Hi' calibrated with O
2
.
Background gas
Error
Background gas
Error
Argon
–0.22%
Halothane
–1.93%
Carbon dioxide
–0.26%
Helium
–0.29%
Note that the error is directly proportional to the concentration of the background gas
in the sample being measured, and in most cases can be ignored.
If you cannot ignore the error, you can use the procedure in Section 5.9.2 and
Appendix A9 to enter a compensation to correct for the error.
☞
Example: If you are measuring O
2
(oxygen) in a background of carbon dioxide
–0.26 should be entered as the cross interference offset.
☞
A full list of cross-interference offsets (O
2
measurement errors) are given in
Appendix A9 For a control measurement the offset should be taken from the
20 °C column and for a purity measurement use the 60 °C column.
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