Gas Purity mode shows inaccurate helium value in near-pure nitrogen
Gas Purity mode may show reduced accuracy when measuring gas mixtures with very low helium content. This article explains why this occurs and what level of precision can be expected.
Possible causes
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Very low helium concentration close to the detection limit
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Similar speed of sound (VOS) values between gas components
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Natural precision limitations of Gas Purity mode
Explanation
Gas Purity mode determines gas composition based on differences in the speed of sound between gas components. When measuring mixtures such as 99% nitrogen and 1% helium, the helium content is extremely low and close to the practical detection limit.
Because nitrogen and helium create only a very small measurable difference at such low concentrations, the calculated helium value may appear unstable or less accurate.
This is a limitation of the measurement principle and does not necessarily indicate a malfunction of the analyzer.
What to expect
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Reduced precision at very low helium percentages
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Greater deviation in the middle of the calculation range
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More stable results when measuring mixtures with higher helium content
When to contact service
If measurement results appear significantly incorrect even with higher helium concentrations or after recalibration, please contact an authorized Divesoft Service Point for further diagnostics.
You can find your nearest authorized service location on our Service Centers page.