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W-CRM working mixtures

W-CRM working mixtures are calibrated gravimetrically and have a lower metrological quality than G-CRMs. W-CRMs are prepared individually according to the reference standard ISO 6142, but the calibration procedures are less stringent than those used for the production of G-CRMs and, consequently, their uncertainty is higher.

The certified value is traceable, through an unbroken chain of comparisons, to the national mass samples certified by Primary Metrology Institutes or Accredited Calibration Centres. Following the preparation, the gravimetric concentration of the mixture is analyzed with the aim of confirming the result.

The uncertainty certified is calculated on the basis of the mixture production process; this uncertainty may vary, depending on the requested concentration, and can ranging between 1 and 6%. W-CRMs are also available as a multi-component gas mixture in line with the compatibility constraints due to the chemical-physical characteristics of the gases.

The main recommended applications are:

  • verification of measurement processes in the area of gas analysis.

Working standard