ABB EasyLine Series Instructions For Installation Start-Up And Operation page 26

26 EasyLine EL3000 Series Commissioning Instructions
Test Gases
Purge gas
Gas Connections
Installation and sample conditioning
Reference point (= electrical zero)
Clean ambient air; its oxygen concentration can be calculated from the
value for dry air and the factor for the consideration of the water vapor
content.
Example:
Water vapor content at 25 °C and 50 % relative humidity = 1.56 Vol.-% of
O  factor 0.98
H
2
Oxygen concentration = 20.93 Vol.-% of O
End-point
Test gas with oxygen concentration in the smallest measurement range
(e.g. 2 ppm O in N )
2 2
NOTES
The pressure ratios at reference point and end-point must be identical.
Notes for checking the reference point and end-point must be considered.
If a housing purge is selected (only in IP54 version), purging may only be
carried out with air (not with nitrogen) as the ambient air serves as a
reference gas.
see section "ZO23: Gas Connections"
ATTENTION
The ingress of liquids into the analyzer module can cause serious
damage including destruction of the sample cell.
NOTE
The following information on installation and the sample conditioning
must be considered for the measurement and the execution of controlled
calibrations (manual, automatic and externally controlled calibration).
Manually operated cocks and valves must be replaced by controlled
valves suitable for the oxygen trace measurement, as required.
 0.98 = 20.6 Vol.-% of O
2 2