26  EasyLine EL3000 Series Commissioning Instructions 
 
Test Gases 
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 
H
2
O  factor 0.98  
Oxygen concentration = 20.93 Vol.-% of O
2
  0.98 = 20.6 Vol.-% of O
2
 
End-point 
Test gas with oxygen concentration in the smallest measurement range 
(e.g. 2 ppm O
2
 in N
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. 
Purge gas 
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. 
Gas Connections 
see section "ZO23: Gas Connections" 
Installation and sample conditioning 
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.