Centre for Mass and Pressure
Contacts:
Centre for Mass and Pressure:
Ing. Dušan Trochta
Director of the Centre
phone: + 421 2 60294 214
e-mail: trochta@smu.gov.sk
Alena Michňáková
Secretariat
phone: + 421 2 60294214
e-mail: michnakova@smu.gov.sk
MASS LABORATORY
Quantity
The Weight denotes a quantity of the same natures: the weight of a body is the standard weight of a body is the product of its mass and the standard acceleration due to gravity.
Unit
The basic unit kilogram (kg) is the unit of mass. It is equal to the Mass of the International prototype of the kilogram which kept at the BIPM. Other units used are gram (g = 10-3 kg), miligram (mg = 10-6 kg) and ton (t = 1000 kg).
Tasks of the laboratory
The main tasks of the Laboratory are research and development to the realisation and dissemination of the unit of mass, the kilogram.
International comparisons
The SMU Ptlr standards are calibrated in BIPM Sevres during the 20 years period.
1998 - Comparison measurement within PHARE Programme (under command of NPL, GB) of the SMU mass standards (5 kg, 1 kg, 200 g, 50 g, 10 g).
1998 - CCM 5 Key Comparison BIPM for calibration of mass scale.
2000 - COOMET Comparison measurement, Project No.127 of compare of the two 1 kg standards value.
Available metrological services
Calibration of sets of weights: accuracy class E1 (range 1 mg - 1 kg), accuracy class E2 (range 1 mg - 50 kg).
Verification and calibration of fine balances of I. and II. accuracy classes in the range up to 50 kg and up to 1000 kg.
Methods of measurement:
The SMU has two Pltr mass standards, which are verified in BIPM Serves, compared to the international kilogram prototype copies. At the SMU Mass Laboratory the mass unit value is transfered from Ptlr standards to stainless steel mass standards of 1 kg (direct comparison method at balance Mettler AT 1006) and the mass scale is calibrated in the range from 1 mg - 100 kg.
During the verification of standards and working weights the expanded uncertainties of determination of weight mass are lower than 1/3 of maximum permissible errors by OIML R111.
Expanded uncertainty is expressed as double value of combined standard uncertainty defined in GUM. At the calibration of balances of I. class accuracy (analytical balances) it is possible to reach uncertainties of mass determination of built in weights equal to E2 class accuracy of working weights.
Supplementary activities
Evaluation of pattern approval of balances of I., II. and partly of III. accuracy classes uo to 1000 kg. Providing of production and verification of mass standards and working weights of E2 accuracy class and production of standard balances of hightest accuracy classes up to 1000 kg (mechanical knives balances and electro-magnetic force compensation balances with flexure strips).
Instruments in use
The National Mass Standard consists of 1 kg Ptlr Mass standards (compared to the international standards in BIPM Serves) and electronic mass comparator Mettler AT 1006 with device for air density determination (Klimet A 30). For the calibration of weights are used the following reference Mass standards and balances:
- 1 kg secondary mass standards;- sets of working standards from 1 g - 500 g made of steel with density of 8 g·cm-3 (E1-OIML);
- Pt standards from 1 mg - 500 mg and sets of steel standards from 1 g - 10 kg (E2-OIML);
- the Mass standards sets up to 50 kg and the total load of 1000 kg (20 pieces of 50 kg) of stainless non-magnetic steel;
- SMU mechanical standard balances from 1 kg - 10 kg (s = 0.05 mg), these standard balances works by method without separation of knives from bearings and with constant load at the weights exchange, simutaneous calibration of two weight sets;
- the standard comparator balances of 100 kg ( s = 1 mg, toploader type with built - in weights, Cu-Be flexures, ± 100 g of electromagnetic force compensation and lifting/loading controlled mechanism);- computer controlled automatic weighting devices for calibration of sets of weights: ranges - from 1 kg to 100 g (with Mettler AT 1005), from 100 g to 1 g (with Mettler AT 106), from 1 kg to 10 kg (with Sartorius CC 10000), from 1 g to 1 mg (with sartorius CC 20).
Each device has a vertical pan below the balance. The pan is for 6 weights individually loaded in necessary combination (by calibration schemes).
DENSITY LABORATORY
Quantity
Density of body p is a derived physical quantity which defined as a rate mass of body m to its volume V: p = m/V.
Unit - kg/m3. Other used units are g/cm3 = 10-3kg/m3 and mg/cm3 = kg/m3.
Methods of measurement:
- standards areometers are calibrated by method of hydrostatic weighing in a reference liquid (density of reference liquid -nonane- is stated by the hydrostatic weighing of quartz divers). Uncertainties of data determination of areometric scale are not hinger than: 0.04 kg·m-3 (for d = 0.1 kg·m-3), 0.04 kg·m-3 (for d = 0.2 kg·m-3), 0.03 % (d = 0.1 %), 0.04 % ( d = 0.2 %), 0.05 % (d = 0.5 %);
- ordinary areometers are verified by the direct comparative method in accordance with SMU working procedures (comparing them to standards in reference liquid);
- vibration densimeters: coefficients of calibration function are determinated by least squares method.
Instruments in use
The National density Standard consists of sets of quartz devers, which volume is stated by the method of hydrostatic-weighing - coming out from the redistilled water density. The measuring device of: analytical balances Mettler (installed at vibration pillar, temperature stability of ± 0.5°C) and mass standards, thermostatic bath Tamson with facilities, device for air density measurement, thermometers, device for water preparation.
Vibration densimeters are calibrated by a reference liquids at semi automatic device for determination of liquid density by hydrostatic weighing. The device under computer control loads and lifts a quartz diver to balance suspension. From balance reading the liquid density is determined.
VISCOSITY LABORATORY
Quantity
Dynamic viscosity is a derived physical quantity which defines a resistance at liquid flow. Dynamic viscosity is defined as a ratio of shear stress to shear rate. Kinematic viscosity is defines as a ratio of the dynamic viscosity to density.
Unit - dynamic viscosity: Pa·s; kinematic viscosity: m2·s-1.
Tasks of the laboratory
The main tasks of the laboratory are research and development for the realisation and dissemination of the unit of viscosity.
International comparisons
ASTM Project D.02.07.A
DUNAMET Project No. D22
EUROMET Project No. 415 - EUROMET.M.V-K3 - key comparison.
Methods of measurement:
The primary standards are calibrated by the step-up method, using the value of the kinematic viscosity of the redistilled water at temperature of 20 °C. The viscometers of higher nominal values are calibrated by direct comparison with viscometers of lower nominal value.
The lower order standards and working instruments (capillary viscometers) are calibrated by the direct comparison with SMU standard viscometers.
Falling Ball and Rotational Viscometers are calibrated by using of certified reference liquids which are traced to the national standard of viscosity.
Instruments in use
The National standard consists of two sets of Ubbelohde capillary viscometers with 500 mm capillary length and two sets of Ubbelohde capillary viscometers with 400 mm capillary length. The measurement device consists of temperature controlled bath with accesories (heating circulator and immersion cooler), Pt25 thermometer, device for water preparation (reference liquid for derivation of scale of kinematic viscosity), computer controlled automatic measuring device for efflux time measurement and measurement control. The standard device is computer operated and process of measurement is free programmable and fully automated by the set of bistabil electromagnetic valves (four valves for each of 8 viscometers in the bath).
The efflux time measurement is realized by swiching on/off the counter, when liquid level passes by the position of optical sensors. Sensors position is adjustable to coincide with ring marks of viscometer.
LOW ABSOLUTE PRESSURE LABORATORY
Quantity - pressure and flow under vacuum and molecular flow conditions.
Unit - Pa, Pa·m3·s-1.
Tasks of the laboratory
The main task of Laboratory is the realisation of a low absolute pressure, parcial pressures and small flows.
Methods of measurement:
- method of dynamic expansion is used to increase the National Standard range to 10-6 to 10-7 Pa. The dynamic expansion is realized by flow through members with known conductivity.
Instruments in use
National Standard - Compress mercury vacuum gauge of McLeon type (range 1 kPa - 10 mPa, combined standard uncertainty from 0.1 % to 1.2 %), stainless steel construction (decreases error caused by electrostatic charge arising from mercury motion in a capillary), glass capillary d = 8 mm, 80 kg mercury, construction eliminates the Ishii effect. Mercury column height is red by telescope with readability 0.01 mm.
Capacitive vacuum gauge with three sensors of 100 kPa, 10 kPa, 1 Pa.
Apparatus for dynamic expansion in the range 10-2 to 10-6 Pa.
Quadrupole mass spectrometer.
Apparatus for glass pressure increase depends on time in known volume.
Set of liquid flowmeter.
PRESSURE LABORATORY
Quantity - pressure.
Unit - Pa.
Tasks of the laboratory
The principal task of the laboratory is an establishment of the National pressure standard.
International comparisons
COOMET project 115/RU/95, EUROMET project No. 439.
Methods of measurement:
- all the pressure balances are routinely calibrated using the crofloating methods fllowing the principles described in the Laboratory calibration procedure that corresponds the OIML recommendation No.110. The EA G26 guide can ce used if the client wish to calibrate his instruments following the principles based on this document;
- the pressure transducers and transmitters are calibrated following the procedures included in the Laboratory calibration procedures following the principles included in the EN 770 standard;
- all the other instruments are directly calibrated by the corresponding laboratory standard following the Laboratory calibration procedure.
Supplementary activities
Special pressure guges calibrations according the client's requirements are available. Special pressure measurements, pressure measurements instruments pattern tests and pattern approval, pressure measurements instruments metrological assessments, calibration laboratory assessment and calibration laboratory staff training is available as well.
Instruments in use
The custom made oil operated piston gauge National Standards consisting of a group of piston cylinder units operating in the range (0.2 - 6) MPa, which effective areas were determined from dimensional measurements. The custom made oil operated piston gauge standards consisting of a group of piston cylinder units operating in the range (10 - 100) MPa traceable to the National Standard. The custom made gas operated piston gauge standards consisting of a group of piston cylinder units operating in the range (0.2 - 7) MPa traceable to the National Standard.
A set of all-purpose piston - cylinder units that can accommodate various manufactures piston - cylinder units for calibration purposes.
Water column micromanometer operating in the range (0 -1.5) kPa or (0 -3) kPa traceable to the National Standard.
All the pressure balances can be calibrated with the combined standard uncertainty lower than 50·10-6.
