ATA Pro
Technical Manual
Int. Approved
Document ref: HEL-810-12
December 2017
Page 6 of 27
Copyright © 2017 Analox Ltd. All Rights Reserved.
Commercial in Confidence
3. It is possible that at very high altitude normal calibration is not
achievable. In this event you must ascertain the actual pressure in BAR
and multiply the atmospheric oxygen percent (20.9%) by this pressure
and set the reading during calibration to the calculated level (this is the
surface equivalent oxygen percentage). An altitude correction chart is
shown for reference on
page 22. When you measure the level of oxygen
in the sample you must divide the reading by the same atmospheric
pressure value to obtain the true percentage of Oxygen in your sample.
For Example: At an atmospheric pressure of 0.8bar, the surface
equivalent oxygen percentage is
20.9% x 0.8 = 16.7% O2 Surface Equivalent. If the reading you then
obtain from your sample is 32.0% you must divide this by 0.8 to obtain
the true Oxygen percentage, 32.0/0.8 = 40.0% O2 True Percentage.
WARNING
The analyser is sensitive to Oxygen partial pressure.
Calibration must always be carried out at the same
atmospheric pressure as Oxygen measurement.