The activities carried out at Mass Metrology Department deal with both mass and related quantities, such as volume, density, flow, fluid viscosity and air speed. In addition one IMGC branch unit ("Fluid dynamics" located at the Department of Aeronautical and Space Engineering, Politecnico di Torino) has been part of this Department since 2002. In the field of the JCGM activity, Supplement 1 to the GUM is now almost ready for publication. This is expected in 2006.
Two prototype artifacts, Hollow and Tube, were constructed and preliminary weighings were carried out in view of volume measurement. The artifacts are intended for the direct measurement of air density. Therefore, their masses should be as close as possible, and their volumes as different as possible. Problems arose with the home-modified 10 kg balance, which needed maintenance by the manufacturer and subsequent modifications to the shaft joints. The platinum-iridium prototype no. 76 was taken to the BIPM for re-calibration, in view of a key comparison. The results of a previous key comparison were made available, showing excellent performance.
Hollow and Tube compared to a 2 kg standard.
The new balance MT AX1005, completely automatised and equipped for hydrostatic weighings, was installed in an enclosure of glass and aluminium, improving thermal insulation and stability. The balance was used to repeat the hydrostatic comparisons between all our solid silicon standards. The results confirmed the discrepancy between our reference standard and those of the PTB and NMIJ. We corrected the uncertainty of our results in the key comparison D-K1. To restore the coherence of reference standards, the silicon sphere AVO#2, calibrated interferometrically at the PTB in 2005, was temporarily adopted. The new balance was also used in calibration activity, which resulted in four certificates.
The activity carried out dealt with the metrology of viscosity, density and volumetric glassware. Some international programmes involved the group in coordinating the regional key comparison EUROMET Project 702 "Comparison of the calibrations of high resolution hydrometers for liquid density determinations", participating in the CCM.FF-K4 "CIPM Key Comparison for Volume Intercomparison at 20 L and 100 mL" and setting up a bilateral comparison with the Portuguese metrological institute (IPQ),(EUROMET Project 858). In addition to the dissemination work, two similar new hydrostatic apparatus for liquid density determination were developed. The apparatus are completely automated through electronic controls and software designed for running the weighing and acquiring the data from the balance. One of them was sold to IPQ. At the end of 2005, collaboration with ENEA and Scandura-Milano started to set up a new density laboratory at the ENEA C.R. Trisaia.
The cell with the sphere and the suspension.
In addition to standardization and dissemination work, a comparison of gas flow measurements was carried out successfully between Italy and Switzerland (EUROMET 852). A G25 rotary piston gas meter was calibrated against four provers of different size and type in the same range of air flowrates (0.3 to 25 m3/h). The comparison highlighted the improved performance of piston provers as compared to the traditional bell provers (both NMIs having pioneered in the past the construction of large piston provers of their own design). At the request of the Istituto G. Tagliacarne (Roma), four training courses in liquid volume measurements were delivered to about 60 legal metrology officers serving at many Chambers of Commerce in all parts of Italy.
Calibrating a gas meter by means of the 1 m diameter piston prover.
Under a contract with Alcatel Alenia Space (AAS-I, Italia), a project is in progress to develop a pressure regulator and a thruster to be used in a “cold gas propulsion system”, both adopting the piezo technology. The first prototype of the thruster was built and is now ready for the qualification test campaign, while the prototype of the pressure regulator is in the construction phase. A second project with AAS-I was also initiated to design two main components (piezo-pump and piezo-valve) of the caging system in the LISA-Pathfinder ESA program: the first prototypes gave encouraging results, although some of the strict requirements are still to be met. The group also participated, together with colleagues from Politecnico di Torino, in the Regione Piemonte's call for tenders with a proposal of a theoretical and experimental study on low-force thrusters for space applications: the proposal was selected and will be financed throughout the 2006 – 2008 triennium.
Pressure regulator prototype.
The upgrade of the national standard of air speed continued, improving the traceability of measurements to determine the translation speed of the carriage of the aerodynamic towing tank. A more accurate uncertainty analysis of all plants, which constitute the national standard of air speed, was developed. Moreover, the development of its numerical capabilities of modeling compressible flows of rarefied gases, to determine the performances of a nozzle for space propulsion, was carried out in cooperation with AAS-I. The working group, that cooperates on this project, was financed with a grant from the Regione Piemonte.
Density distribution in a nozzle in the presence of rarefied gases.