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A Helium analyzer is an instrument used to identify the presence and concentration of helium in air or a mixture of gases.
A Helium analyzer is an instrument used to identify the presence and concentration of helium in air or a mixture of gases.
Applications
A helium analyzer is typically used in the following applications: * Technical Scuba Diving: InTechnical diving
Technical diving (also referred to as tec diving or tech diving) is scuba diving that exceeds the List of diver certification organizations, agency-specified limits of recreational diving for non-Professional diver, professional purposes. Technica ...
where breathing gas mixtures known as Trimix comprising oxygen
Oxygen is a chemical element; it has chemical symbol, symbol O and atomic number 8. It is a member of the chalcogen group (periodic table), group in the periodic table, a highly reactivity (chemistry), reactive nonmetal (chemistry), non ...
, helium
Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...
and nitrogen
Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...
are used, it is necessary to know the fraction of helium in the mixture to reliably calculate decompression schedules for dives using that mixture.
* Leak Detection: Helium gas analyzers are used to detect helium escaping from pressurized systems, identifying microscopic leaks in vacuum chambers, cryogenic equipment, and pipelines.
* Semiconductor Manufacturing: Ultra-pure helium analysis detects parts-per-billion impurities during chip fabrication, ensuring product quality.
Thermal conductivity principle
Portable instruments for the analysis of helium content of breathing gas mixtures may be based on a thermal conductivity sensor ( katharometer). These sensors can be very stable and maintenance free and also highly reliable and accurate. A typical thermal helium analyser comprises two chambers, each with an identical thermal conductivity sensor. One chamber is sealed and is filled with pure helium as the reference gas, and the other receives the sample gas. The difference in thermal conductivity of the reference and sample gases is measured and converted into a concentration value by the electronic circuitry in the instrument. The system is inherently stable and when precise temperature compensation is made, the system is more than adequately accurate forbreathing gas
A breathing gas is a mixture of gaseous chemical elements and compounds used for respiration. Air is the most common and only natural breathing gas, but other mixtures of gases, or pure oxygen, are also used in breathing equipment and enclosed ...
analysis. Accuracy and display precision is typically within 0.1%, and accuracy within 1% is considered sufficient for most decompression algorithms
There are several categories of decompression equipment used to help divers decompress, which is the process required to allow divers to return to the surface safely after spending time underwater at higher ambient pressures.
Decompression o ...
.
The thermal conductivity of nitrogen and oxygen are very similar, and that of helium very different so that the ratio of oxygen and nitrogen in the mix is relatively unimportant, and need not be compensated. This allows a direct reading of helium fraction from these instruments. However, for greater accuracy and compensation to oxygen cross-sensitivity, some instruments include an oxygen cell, and in these cases can generally give a full helium and oxygen analysis of the mixture simultaneously.
Speed of sound principle
Helium content may also be determined on the basis of measuring the speed of sound in the analyzed gas mixture. The speed of sound depends on the mixture of gases and the temperature of the mix; in the analysis of trimix the speed of sound can be described by a non-linear function of temperature, oxygen content and helium content, and thus the content of helium can be determined by measuring the speed of sound through the mix, the temperature of the mix and its oxygen content.See also
*References
External links
* {{Underwater diving, divsup Breathing gases Underwater diving safety Measurement Diving support equipment