Gas mixtures with the gravimetric method G-CRM - SIAD Società Italiana Acetilene e Derivati
Gas mixtures with the gravimetric method G-CRM
Gas mixtures with the gravimetric method G-CRM - main
G-CRMs are gas mixtures calibrated gravimetrically according to the standard ISO 6142. Metrological traceability derives from the mass samples calibrated by a Primary Metrological Institute or by an Accredited Centre used for preparing the mixtures.
The calculation of the concentration and the uncertainty of the mixture takes into account: the choice and quality of the raw materials and the mother mixtures; the masses used for calibrating the balances and their performance; the calibration environmentalconditions; and the preparation procedure with all the uncertainties relating to the weighing process. All the individually prepared mixtures are analytically verified.
The validation analysis follows the guidelines of ISO 6143, which provides for a three-point instrumental calibration using the method of generalized least squares (GLS). The samples used for instrumental calibration are metrologically traceable mixtures produced by the Centre (G-CRM or CRM) or certified by a Primary Metrological Institute. The G-CRM mixture is then traceable to the mass and all the mixtures are also validated by analysis with respect to traceable mixtures. The validation process is a distinguishing feature of the Centre's mixtures to further support the high quality of these mixtures.
G-CRM mixtures, on a par with CRMs, are characterized by the best possible preparation tolerance with current technology, and by very small relative extended uncertainties. G-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:
- the calibration of equipment requiring traceable measurement performance (legislative parameters, specifications of supply, etc..) and low uncertainties.