Air Monitoring

  • The high performances automated gas diluter/calibrator from LNI Swissgas

The high performances automated gas diluter/calibrator from LNI Swissgas

Feb 14 2018 Read 1257 Times

An accurate measurement of a gas concentration involves several parameters like sampling, measurement technique, analyser, operator and calibration.

In some cases, very high accuracy is required. For instance, if a manufacturer claims for a 1% accuracy on a gas analyser, he needs to have calibration tools which support this specification statement.

The Sonimix 2106 works according one section of the ISO 6145 norm called "Preparation of calibration gas mixtures using dynamic methods -- Part 6: Critical flow orifices".

The principle of this technique is the dilution of a gas by a complementary gas like nitrogen or air. The use of gas mixtures as parent gases is also possible.

A sonic nozzle is a very small Venturi tube (convergent-divergent) where specific inlet-outlet pressure conditions generate a shock wave at the minimal section and where the gas reaches the local speed of sound. At this stage the flow is independent of downstream conditions. A very high precision pressure regulator is used at the gas inlet of stream to maintain a very precise mass flow rate.

Dilution ratios up to 1:1000 are achieved in discrete increments by the combination of several sonic nozzles.

Calibration with dynamic methods have several benefits: cost reduction (removal of cylinders with several concentrations), flexibility to generate any concentration quickly, convenience, automated generation of concentration sequences.

Additionally, the sonic nozzle technology provides several unique benefits:

  • Metrological superior performances – flow uncertainty of each channel below 0.2%, a gas mixture is generated with a relative expanded uncertainty of 0.5 % (coverage factor k = 2) on the concentration and throughout the whole dilution range
  • No warm up time – working conditions and full specs are reached immediately without dead time
  • Long term stability – as the setup is very simple, the mechanical stability last for several years
  • Trusted metrology results – LNI Swissgas is ISO 17025 is accredited and complete calibration process and report are provided not only for new devices but across it's whole lifetime
  • Flow rate is constant - not affected by downstream flow or pressure disturbances
  • Extended dilution capability – a second device can be diluter can be mounted in serial to expand the dilution ratio up to 1/100000
  • Corrosive gas option – components made of gas into the gas path insure trouble free operation even with aggressive gases
  • High reliability – minimal number of mechanical and electronical devices reducing the risk of troubles

The device includes quick lines purge routines, reducing significantly the stabilization time when applying large dilution ratios changes.

The intuitive menu appear on a color touchscreen and includes several functions as well as a diagnostic function to check all internal and external lines of the instrument for complete system verification.

Ethernet and USB ports allow to communicate easily with the Sx2106 for different purpose such as configuration, data download, software update, etc.

For more information about the Sonimix-2106 please click here.

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