User Manual SERVOPRO Plasma Trace N
2
Analyzer
8.0 START-UP
Before ending this section, there is one more thing to consider. Calibration cylinders come with a
certificate attached, confirming the amount of impurities in the cylinder. It is a good idea to find
out how this analysis was done.
Servomex is a good customer of such cylinders coming from different sources of specialty gases.
Sometimes, with three cylinders containing the same quantity of impurities (less than .2 ppm
total difference), each coming from different suppliers, we obtained some surprising readings. In
some cases, there was a difference of more than three times the quantities stipulated on the
certificate from cylinder to cylinder.
Beware of this.
See our application note "RECOMMENDED GAS SAMPLING HARDWARE AND
TECHNIQUE FOR LOW TRACE N
2
MEASUREMENTS IN ARGON".