IMEKO Event Proceedings Search

   

Page 824 of 936 Results 8231 - 8240 of 9356

Luis M. Peña, J. Carlos Pedraza
A new image processing system for hydrometer calibration developed at CENAM

The present work illustrates the improvements made to the hydrometer calibration sys-tem of CENAM, the NMI of Mexico, making use of an image processing technique to align the scale mark of the hydrometer to the surface of the liquid where it is immersed, reducing the variability in the apparent mass determination during the hydrostatic weighing in the calibration process, decreasing the relative uncertainty of calibration (k = 2) from 1 x 10-4 to 5 x 10-5 or better.

Christian Buchner
Automatic testing facility for determining liquids and solids density and determining the volume of E1 weights

In cooperation with Sartorius AG in Goettingen and the Vienna University of Technology, the Austrian Federal Office of Metrology and Surveying (BEV) has developed a test System for hydrostatic weighing and determining the density of liquids and solids, whereby mass comparators are automatically loaded alternately with weights and submerged plummets. With the load alternator for weights and plummets, the density of a liquid on one side and the density of a submerged solid (and therefore its volume) on the other side can be determined hydrostatically via direct comparison with Standard plummets and the applied substitution weights.
To determine consecutively the volume of E1 weights and plummets, additional a fully automatic handling system for a 1-kg mass comparators, a volume comparator was developed. Thus, the hydrostatic weighing principle can be applied for serial volume determination on masses from 1 g to 1 kg by direct comparison with a single volume reference (e.g., a silicon sphere). This prinziple is implemented with a newly developed, fully automatic insertion mechanism for both completely submersed weights and substitution weights.
Both Systems are used for the dissemination of density and volume by BEV as well as for testing and calibrating of liquids and plummets and determining the volume of weights in connection with the determination of mass scale.
The volume comparator is also used in other metrology institutes and in accredited calibration laboratories.

S. Lorefice, A. Malengo, M. Caravaggio, L. Cianciotta
Design of an automatic apparatus for the calibration of on-line densimeters

The design and the expected performance of a new apparatus suitable to satisfy the traceability requirements in the density field is here presented. The apparatus is mainly intended to measure liquid density range between 500 kg/m³ and 3000 kg/m³ and to evaluate the performance of on-line densimeters during the actual use, i.e. the same process liquid under similar flow conditions. Details about the hardware components of the system and the software programs are also given. By using an instrument not specifically selected and calibrated for the intended working conditions, the value of uinstr(ρ) = 0.20 kg/m³ instr u is the lowest expected uncertainty of density measurements of fluids. However, higher accuracy can be established for the selected reference instrument by the use of the same fluids employed in the process at the usual operative conditions and whose densities are certified by national metrological institutes (NMIs) or accredited laboratories.

Luis O. Becerra, Dalni Malta, Luz. Ma. Centeno, José Julio Pinheiro
Solids volume by hydrostatic weighing comparison between CENAM-Mexico and INMETRO-Brazil. SIM.7.34-B

This paper presents the results obtained for a SIM comparison between CENAMMexico and INMETRO-Brazil in volume of solids by hydrostatic weighing measurements. In this work are presented a scheme of measurements, and the systems used by the National Metrology Institutes.
The travelling standards were two spheres made of different materials (stainless steel and glass) with approximated diameter of 15 mm each.

Horst Bettin
Temperature control in the µK range for density measurements

A temperature controller for density measurements is presented that allows temperature stabilities of about 10 µK to be achieved near 20°C. The controller consists of a function generator, a thermistor in a Wheatstone bridge, a differential amplifier, a lock-in amplifier, a PC and a power source for the heater. Two of the controllers are also used to stabilize an electronic temperature fixed point at 20°C that will help to compare the realizations of the 20°C temperature in different laboratories with an uncertainty below 0.5 mK.

Sari Semenoja, Kari Riski and Leena Stenlund
Determination of Air Density with Buoyancy Artefacts

When comparing mass standards with large volume differences the density of air is one of the largest uncertainty components for mass. The air density can be determined by direct weighing using buoyancy artefacts or it can be calculated from the CIPM 81/91 formula. A small relative difference (about 6·10-5) between these two methods exists. The aim of the present work is to verify this difference and to gain experience on vacuum weighing and on the stability of weights. Two buoyancy artefacts with different volumes were utilized. The artefacts were compared in vacuum and in air. From the weighing results air density was calculated and compared with the CIPM formula. The following value for the relative air density difference was obtained 4 x 10-5 (u=7 x 10-5).

Carlo Ferrero, Luciano Bianchi
The SIT activity to disseminate physical quantities in Italy: calibration of material testing machine intercomparisons

One of the most important activities at European (EA) and National level of the National Accreditation Body (NAB) is the organisation of a series of interlaboratory comparisons (ILC), to verify the measurements capability of the accredited Laboratories. In 1999, 2001, 2002, 2004 four ILCs, for the calibration of material testing machines, was organised in Italy by SIT. In the present paper the main results obtained during the ILC are discussed, in particular a regression analysis was applied to evaluate the differences on the repeatability and accuracy given by the different laboratories.

C. Ferrero
Dissemination of the force unit in Italy: intercomparison results up to 20 kN

In the field of calibration, Italy participates to the European framework with SIT(Servizio di Taratura in Italia), which grants accreditation through the verification of the correctness of the calibration of the measurement instruments with reference to the National Standards maintained by the Metrological Institutes INRIM and ENEA.
One of the most important activities of the National Accreditation Body (NAB) is the organisation of a series of interlaboratory comparisons (ILC), at European (EA) and National level, to verify the measurements capability of the accredited laboratories.
In 2004 and In January-February 2005 ILCs, for the calibration of force transducers, were organised in Italy by the SIT with the INRiM (formerly IMGC-CNR and IEN) as pilot laboratory. At the experimental ILCs participated four accredited Calibration Laboratories. The relative deviation up to 20 kN of the calibration machines, from the INRIM standard deadweigh machines (DWM), were allways less than +/- 50 10–6.

T. Bartel
Statistical Analysis of 2 MN and 4 MN Force Range Key Comparisons

The factors contributing to the uncertainty are discussed for the measurements that were conducted for the 2 MN and 4 MN force values of the very high force key comparison administered by the Comité International des Poids et Mesures (CIPM). Details of the statistical analysis by the pilot institute, NIST, are provided. Various options for calculating the reference values and degrees of equivalence are presented, accounting for the uncertainty differences associated with the comparison force transfer standards and with the force standard machines of the participating National Metrology Institutes (NMI).

Laurence Brice, Andy Knott, Alan Wilson
Continuous calibration of force transducers

A technique for calibrating force transducers under dynamic input conditions is reported and evaluated. The output of a test transducer is determined at a number of points on an applied input force ramp by comparison with a calibrated reference transducer connected in series, enabling the output sensitivity of the test transducer to be determined. Experimental results show that transducer output values obtained using this dynamic calibration technique are in agreement with those obtained using a static calibration procedure to within 0.05%. This continuous calibration technique provides an alternative to calibrating the transducer statically, greatly reducing the time required for transducer calibration. Investigation of the creep characteristics of a range of test transducers demonstrates that creep performance is a major contribution to agreement between transducers in continuous calibrations, leading to possible techniques for the correction and subsequent improvement of calibration results.

Page 824 of 936 Results 8231 - 8240 of 9356