INM LABORATORIES

• LENGTHS LABORATORY
• MASS AND RELATED QUANTITIES LABORATORY   

• MASS Group
• PRESSURE Group

MASS GROUP

Main activities:

• Preservation, maintenance and use of the national mass measurement standard, the National Prototype Kilogram no. 2
• Dissemination of the mass unit from the National Prototype of the  Kilogram to the reference standards and further down to working standards, between 1 mg and 1000 kg.
• Preservation, maintenance and use of the reference standard for the hectoliter mass (the bulk density of cereals).
• Realization and dissemination of the hectoliter mass unit for cereals.
• Research for the development of the national and reference measurement standards and to ensure the traceability to the SI units and in the field of mass metrology.
• Preparing written standards, technical norms and procedures used in the calibration, verification and testing in the field of mass metrology.
• Participating in international comparisons measurements.
• Participating in national inter-laboratory comparisons.
• Performing tests as part of type evaluation and pattern evaluation for mass measures (weights), weighing instruments and instruments measuring the hectoliter mass.
• Cooperation with other Romanian institutions and similar institutes from abroad.
• Consultancy and training on issues related to the theory and practice of measurements.

Mass. The Prototype of the Kilogram.

Mass is one of the fundamental quantities of mechanics. The notion of mass is closely related to the notion of matter, as mass is one of the fundamental characteristics of matter.

Mass can be defined as a scalar magnitude that measures the inertia of bodies.

In the International System of Units, the unit of measurement for mass is the kilogram. It is defined as “the mass of the International Prototype of the Kilogram” and was adopted as the unit of measurement for mass by the General Conference on Weights and Measures (CGPM) in 1889.

The International Prototype of the Kilogram is kept at the International Bureau for Weights and Measures (BIPM), at Sèvres, near Paris, France, and is made of a platinum (90%) and iridium (10%) alloy. It has a density of approximately 21,500 kg/m³ and is shaped as a cylinder, with height and diameter equal to 39 mm.

Romania has the "National Prototype Kilogram no. 2", issued by the General Conference of Measures and Weights in 1891. It is kept by the National Institute of Metrology and serves as a reference for the entire activity of disseminating the mass unit in the country.

The National Prototype Kilogram no. 2 is periodically calibrated at the International Bureau for Weights and Measures (BIPM), thus ensuring its traceability to the SI.

The 1 kg mass comparator

In order to compare the 1kg reference measurement standards with the National Prototype Kilogram, we use an automated mass comparator of 1 kg, with resolution 1 μg and repeatability less than 2 μg.

The comparator is connected to an installation that monitors air pressure, temperature and humidity that enables a very accurate determination of air density and to make corrections for the buoyancy effect.  

Dissemination of the mass unit

The calibration operations performed by the INM Mass group are under the Quality System of INM, according to the requirements of SR ISO 17025, which is an internationally recognized system within EUROMET.

Calibration capabilities*)

*) The calibration capability was analyzed within EUROMET and submitted for approval and publication in the BIPM database.

The Mass Laboratory is accredited by the German accreditation body Deutscher Kalibrierdienst (DKD).

The figure shows the accreditation certificate of the Mass laboratory of the National Institute of Metrology; the laboratory is registered as DKD-K-39702.

DKD is a member of European Cooperation Accreditation Body (EA) and a signatory of the multilateral agreement for mutual recognition of calibration certificates.

Calibration intervals and calibration uncertainties which the accreditation was requested for are the most demanded ones by laboratory’s customers.

The following table shows the measuring means, the calibration intervals and the lowest expanded calibration uncertainties for which the Mass laboratory of the National Institute of Metrology may issue DKD calibration certificates:

where: mc – conventional mass

Hectolitre mass of cereals

As all natural products (influenced by the soil, the atmospheric conditions, the storing method), cereals have an infinity of varieties, which can be discerned by visual aspect, by touch, smell, taste, etc. One of the scientific methods for the determination of cereals quality is by measuring their hectolitre mass (bulk density).

Determining the hectolitre mass of the cereals is a rather complicated procedure, as it needs to determine the mass of a quantity of cereals, consisting of a large number of grains, which must always be laid the same way in order to occupy the same volume. This requirement is hard to meet, as the same quantity of cereals can occupy a larger or smaller volume, depending on how the grains settle in the measuring vessel. The issue was solved in the cereal weighing machine, using measuring vessels with standardized shape and size and using a special method for filling the vessel, so that the grains are uniformly laid.

The hectoliter mass of cereals is by definition the mass of that amount of grain required to fill a specified receptacle. This depends not only on the intrinsic quality of the considered cereals, but also on their hydrometric state, on the capacity, size and shape of the container used to measure their volume, and on how it is filled.

The Romanian measurement standard for the hectoliter mass of cereals is the measurement standard 20-liter cereals weighing machine, which serves as a reference for the entire dissemination of this unit in Romania.

International cooperation

Participations in international comparisons:

• International comparisons of mass measurement standards, EUROMET project no. 592 – pilot laboratory: National Physical Laboratory (NPL) from UK (1998);
• International comparisons of 1 kg mass measurement standards within the COOMET program, Project 127/PL-a/97 – pilot laboratory: Central Bureau of Measures (GUM) from Poland (1999);
• International key comparison of 1kg mass measurement EUROMET-MM-K4 ;
• International key comparison of 10kg…100 mg, EUROMET-MM-K2;
• Bilateral comparison, EUROMET no. 742, between the National Institute of Metrology (INM) and the Danish Institute of Fundamental Metrology (DFM), at national mass standard level.

Performing tests as part of type evaluations and pattern evaluations

The Mass group performs tests within the type evaluations and pattern evaluations of measuring means for mass, in accordance with the following norms, international recommendations and standards:

• International Recommendation OIML R111 – for mass measures (weights).
• Governmental Decree HG 617 from 2003, standard SR EN 45501, International Recommendation OIML R76 – for nonautomatic weighing instruments
• International Recommendation OIML R50 – for Continuous totalizing automatic weighing instruments (belt weighers).
• International Recommendation OIML R51 – for automatic catchweighing instruments
• International Recommendation OIML R61, Norm of Legal Metrology NML 3-08-97 – for Automatic gravimetric filling instruments
• International Recommendation OIML R106 – for Automatic rail-weighbridges.
• International Recommendation OIML R107 – for Discontinuous totalizing automatic weighing instruments (totalizing hopper weighers)
• International Recommendation OIML R134 – for Automatic instruments for weighing road vehicles in motion.
• International Recommendation OIML R15, standard SR ISO 7971-2, norm NTM 3-04-76 – for Instruments for measuring the hectoliter mass of cereals

Personnel, positions and contact details

Eng. George Florian Popa, head of Mass group, tel. 334 48 30 / 178, e-mail: popa@inm.ro, georgefpopa@yahoo.com

Eng. Valerică Totu, deputy, tel. 334 48 30 / 178, e-mail: totu@inm.ro, valericatotu@yahoo.com

Eng. Gabriela State, quality assurance manager, tel. 334 48 30 / 178, e-mail: state@inm.ro

Eng. Adriana Vâlcu, , tel. 334 48 30 / 178, e-mail: adriana@inm.ro, adivaro@yahoo.com

S-Eng. pr.  Ion Nistor, tel. 334 48 30 / 161 e-mail: nistor@inm.ro

Tehn. pr. Sterică Baicu, tel. 334 48 30 / 178, e-mail: baicu@inm.ro, baicust@yahoo.com

Tehn. pr. Ecaterina Manea, tel. 334 48 30 / 161, e-mail: cathy@inm.ro

PRESSURE GROUP

National pressure measurement standard

The national pressure standard is represented by the Ruska pressure balance (USA), type 2400, series 21601, with two re-entrant type piston-cylinder assemblies, and a set of weights, with the following metrological characteristics:

• low pressure piston-cylinder assembly
  • range: (0.5…17) MPa
  • effective area: 0.840 091 × 10^-4 m²
  • relative uncertainty of effective area: 3.3 × 10^-5
  • CC 0040/2007 - PTB Germany
• high pressure piston/cylinder assembly
  • range: (5…85) MPa
  • effective area: 0.168 003 × 10^-4 m²
  • relative uncertainty of effective area: 4.2 × 10^-5
  • CC 0041/2007 - PTB Germany
• weights
  • made of non-magnetic stainless steel, consists in 21 pieces
  • mass of weights: between 17.131 kg and 0.008 570 kg
  • relative calibration uncertainty 1 × 10^-5
• work fluid: oil

Reference  standards

Reference standards are represented by pressure balances, with oil or gas (air) as working fluid.

Reference standards with oil take the unit of measurement from the national standard by direct comparison and have the following measuring ranges and relative uncertainties for the effective area:

• (0.1…3,5) MPa; U = 6 × 10^-5
• (0.1…5,5) MPa; U = 6 × 10^-5
• (0.1…7) MPa; U = 6 × 10^-5  *)
• (0.2…35) MPa; U = 6 × 10^-5
• (1…55) MPa; U = 6 × 10^-5
• (2…110) MPa; U = 8 × 10^-5

*) Also used as a transfer standard for international EUROMET comparisons

Reference  standards with air take the unit of measurement from the  standard Ruska pressure balance with the following characteristics:

• piston-cylinder assembly, Serial No. TL1622
• range: (3,5 … 175) kPa
• effective area: 3,357 36 × 10^-4 m²
• relative uncertainty of effective area: 2,4 × 10^-5
• CC  E07010466/1/2007 - NPL United Kingdom
• piston-cylinder assembly, Serial No. C596
• range: (16 … 700) kPa
• effective area: 0,839 650 × 10^-4 m²
• relative uncertainty of effective area: 2,0 × 10^-5
• CC  E07010466/2/2007 - NPL United Kingdom
• piston-cylinder assembly, Serial No. V1621
• range: (0.1 … 7) MPa
• effective area: 0,083 9245 × 10^-4 m²
• relative uncertainty of effective area: 2,4 × 10^-5
• CC  E07010466/3/2007 - NPL United Kingdom
• piston-cylinder assembly, Serial No. G130
• range: (0,1 … 3,5) MPa
• effective area: 0,167 937 × 10^-4 m²
• relative uncertainty of effective area: 2,4 × 10^-5
• CC  E07010466/4/2007 - NPL United Kingdom

Reference measurement standards with air have the following ranges and uncertainties for the effective area:

• (0.0015…0.1) MPa; U = 6 × 10^-5
• (0.01…0.35) MPa; U = 6 × 10^-5
• (0.01…0.7) MPa; U = 6 × 10^-5
• (0.02…1) MPa; U = 6 × 10^-5

Metrological services

Calibration for the following types of measuring instruments:

• pressure balances
• manometers with elastic sensing element
• absolute pressure vacuummeters
• micromanometers with compensation, with liquid
• pressure calibrators
• pressure transducers
• any other instruments for measuring pressure

Verification for the following types of measuring instruments:

• manometers with elastic sensing element for measuring gas or liquid pressure
• manometers with elastic sensing element for measuring pressure in oxygen cylinders
• non-invasive mechanical sphygmomanometers
• tyre pressure gauges for motor vehicles
• pressure transducers

For the full list of calibrations and charges, see the List of measuring means for which the Romanian Legal Metrology performs calibrations, LE 2006.

Ensuring traceability to the SI and laboratory capabilities

The PRESSURE group has traceability ensured to  PTB Germany, for pressure balances with oil, and to NMi Holland, for pressure balances with air.

For pressure balances with oil, traceability was confirmed by the results obtained in the bilateral comparison INM-IMGC, and for pressure balances with air it will be confirmed in the COOMET comparison.  

From the pressure balances, the unit of measurement transferred to other pressure balances, with lower accuracy, to pressure calibrators, manometers with elastic sensing element, transducers, etc.

As for the weights of pressure balances, the laboratory has traceability to the MASS-INM laboratory, accredited by DKD Germany.

The measuring capabilities ensured by the MASS AND RELATED QUANTITIES laboratory – PRESSURE group are shown in Table 1.

Table 1

Personnel, positions and contact details

Eng. Ion Sandu, head of laboratory, tel. 334 48 30 / 148, e-mail: ion.sandu@inm.ro, inm_sandu@yahoo.com

Eng. Iorgu Alexandra, tel: 334 48 30 / 148, e-mail: iorgu_alexandra@yahoo.com

S-Eng. Virgil Buzdugan, tel: 334 48 30 / 176, e-mail: virgilbuzdugan@yahoo.co.uk

Tehn. Dan Mitu, tel: 334 48 30 / 148, e-mail: dan_mytu@yahoo.com

Tehn. Aurel Ioana, tel: 334 48 30 / 176, e-mail: ioana_aurel@yahoo.com

• ELECTRICAL MEASUREMENTS LABORATORY
• THERMOMETRY LABORATORY
• PHISICO-CHEMICAL QUANTITIES LABORATORY
• FLOW QUANTITIES LABORATORY
• TIME AND FREQUENCIES LABORATORY
• OPTICAL QUANTITIES LABORATORY
• ACOUSTICS AND KINEMATICAL QUANTITIES LABORATORY
• IONIZING RADIATIONS LABORATORY