Mass and related quantities

Mass and Solid Density

The laboratory maintains the Mass National Reference Standard, the copy No 62 of the International Prototype Kilogram.  It realizes the mass scale in the range from 1 mg to 500 kg and periodically takes part in the international comparisons, at both European (Euramet) and International (CIPM) levels.

The best relative uncertainty obtained at the kilogram level is about 1.4•10-8.

The laboratory experts collaborate with ACCREDIA - Italian Accreditation Body - and participate in the Euramet and CIPM Consultative Committees.

The research consists in the following activities:

  • improvement of weighting methods in air, vacuum and inert gases;
  • study of cleaning methods and effects on the mass standards stability;
  • study of sorption effects on mass standards during their transfer from vacuum in air and vice versa;
  • analysis of models used for the calibration and utilization of balances.

The laboratory also maintains  the National Reference Standard of density: a silicon sphere of 1 kg mass with relative uncertainty on volume about 8•10-8.

The dissemination is carried out using the hydrostatic weighing method, its measurement range is from 1 cm3 to 6250 cm3.

The hydrostatic weighing system realized by INRIM, is an automatic one which uses a balance with resolution of 10 µg. The liquid in which the hydrostatic weighing takes place is kept at a constant temperature value with an uncertainty less than 0.01 °C.  Such system permits to obtain relative uncertainty levels on the volume and density measurements of 2•10-7.

The density measurement of the solid objects is used for the calibration of the density standards and for the estimation of the purity and homogeneity of materials as well.

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The quantity force has the unit of measurement, as defined by SI, the newton. It's a very important vector quantity in mechanical measurements. The main research activity is devoted to the study and development of primary standards.

The developed and realized standards are primary force  standard machines that realize the definition of force generated by the mass in the Earth's gravitational field.

They are "dead-weight" machines capable of generating forces from 0.5 N to 1 MN with a relative expanded uncertainty of 2•10-5 (0.002%).

On such standards, top researches on influence factors like mutual attraction among the masses, aerodynamic and magnetic effects are carried out.

Other activities are oriented to the multicomponent force measurements for industrial applications and to the development of new build-up force reference standards in the high range (5 MN).


Hardness is a mechanical property of materials non defined as unit in the SI. Moreover, hardness scales are defined, at International level, by the Committee of Weights and Measurements and by the related standards.

The main research activity is devoted to the study and development of primary standards  and to definition of the hardness scales.

National scales are realized by primary hardness standard machines (designed by INRIM) that represent the best achievement of the state-of-the-art of the international definitions realization.

Above the traditional scales (Rockwell, Brinell, Vickers and Knoop), new developments include the realization of Martens scales.

The research activity therefore focuses to the study of the influence effects of the testing cycles in the realization of the hardness scales, to the study of the elastic-plastic properties of materials, to the scale factors in the determination of the aforementioned properties; moreover, the research found application in the development of the instrumentation, in the realization of the measurement standards and for supporting the standardization.

Map of gravity measurements on Mt. Etna (active volcanic in Sicily, Italy)

Earth's gravitational field varies mainly depending on location (latitude, altitude and local mass distribution) and time (lunar-solar attraction).

The research activity is mainly focused on the development and improvement of the metrological characteristics of the absolute gravimeter realized in INRIM (IMGC-02) that carry out the absolute measurement of gravity acceleration through the rize-and-fall free motion of a falling body. The used method is recognized as a primary method by the International Committee of Weights and Measurements.

The instrument is transportable and can carry out on-site measurements with a minim relative expanded uncertainty of 8.4•10-9.

Research is also focused to the study of influence factors, like rotational effect of falling body, pseudo-inertial reference point of interferometric measurements and mutual attraction of the masses of the instrument.

National and international collaborations with other research bodies allow the application of the measurement in several metrological and geophysical areas, such as force, pressure, mass (Watt balance), volcanology, geodesy, etc.

Gas, volume and flowrate

The Laboratory develops researches in the field of gas flow, with the aim of preparing measurements for future needs. The main reasearch topics presently include the development of methods for the measurement of air volume and flow through samplers for environmental applications, dynamic dilution methods for generating gas mixtures, and the study of performance and features of novel gas meters. An interesting project recently completed involved the development of positioning motors for scientific satellites (cold thrusters).

Laboratory of Liquid Flow

The laboratory maintains the national reference standard of volume and liquid flow (water), based on a  gravimetric weighing system. The measurement obtained can be expressed both in mass or volume of the liquid. 

Measurement range is from  0.01 L/s to 7 L/s, with temperature values in the range from 20 °C to  80 °C.

Research consists in the following activities:

  • improvement of the calibration and measurements uncertainties methods,
  • development of the measurement methods of the heating energy, in order to realize a reference standard for this quantity.

The laboratory takes part periodically in the international measurement comparisons.

The best relative expanded uncertainty is of 0.1%.

The laboratory experts collaborate with ACCREDIA - Italian Accreditation Body - and participate in the Euramet and CIPM Consultative Committees.

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Last modified: 05/22/2017 - 11:15