A major factor determining the uncertainty associated with the value of a standard mass at any level is the performance of the mass comparators employed at various levels in the traceability chain. Improvement in the uncertainty of mass standards is thus dependent on the research and developments of better mass comparators. The National Institute for Standard (NIS) Egypt was equipped in 1997 with Mettler AT-1006 comparator to compare masses in four positions. The comparator capacity from 50 to 1000 g is of particular interest, since this range is the range in which the comparisons against the national prototype kilogram are carried out. Controlling software has been adopted to work with the Mettler AT-1006 comparator for driving the balance to execute any comparison scheme. New climatic system for measuring the air density was established for Measuring the ambient parameters and combining them in the well-known BIPM 1990 formula enable measuring of the air density in the laboratory indirectly. The performances of the system were studied as well as an estimation of expanded standard uncertainty calculations were carried out. Improvement in the comparator performance after using the new control software has been achieved and the climatic system.

A new approach to load cell compensation modeling based on a function link neural network is discussed in this paper. It firstly introduces the function-link neural network to compensate both linearity and temperature effect of a load cell. An example is given to illustrate the proposed method. Various of coefficients of this network is discussed including the different compensation results on three functional expansion, the relationship between initial learning step and compensation accuracy and etc. A proper network is worked out to compensate load cell up to OIML C10 degree in this paper. This neural network compensation of the above errors was achieved via micro controller. Results in this paper indicate that with above compensation the accuracy of a transducer could be improved greatly. This approach for sensor modeling is superior to the existing techniques. It has a potential future in the field of measurement.

Since 1980, the different national metrology institutes use the same procedure and formula for air density determination. The formula employed assumes some hypotheses on the composition of dry air and is expressed in terms of its molar mass and the four environmental parameters: air pressure, air temperature and concentrations of carbon dioxide and water vapour. In this formula (known as CIPM-1981/91) recommended by the Comité International des Poids et Mesures, the mole fraction of argon is fixed at 9.17×10^-3. This value is now questioned and new measurements involving different techniques, are of great interest. This paper describes the experimental set-up used to evaluate the concentration of argon relative to that of nitrogen contained in air sampled from mass laboratory. The method uses a flexible capillary tube, maintained at constant temperature, for gas admission. With this system, air from different samples of atmospheric air is introduced into the vacuum chamber to be analysed. Preliminary measurements show that the value of p_Ar/ p_N2 is closer to 1.196x10^-2, given in some imeko_proceedings, than the value of 1.174x10^-2, used in the current method for air density determination. In the future, comparison between argon and oxygen concentration will allow a more precise measurement with regard to the existing values.

The force unit generated by the 2 MN hydraulic force standard machine in KRISS was changed to Newton from kilogram-force. This paper describes the estimation of the hydraulic force standard machine. First, the machine was compared with a 500 kN deadweight force standard machine in KRISS. The relative deviation between two force machines was less than 2 x 10^-5. In order to estimate the hydraulic force machine in the whole range, we made an intercomparison with a 2 MN deadweight force standard machine in PTB. Intercomparison test revealed that the relative deviation between the KRISS hydraulic force machine and the PTB deadweight force machine is less than 8.1 x 10^-5 in the range of 400 kN to 2000 kN.

This paper describes the development of a 120 kN deadweight force standard machine and its commissioning in late 2003 / early 2004. The rationale for developing a machine of this capacity is given together with details of its design, focusing in particular on the scalepan and weightstack arrangements. The calibration of the masses is described and an uncertainty budget for the force generated by the machine, resulting in an expanded uncertainty of ±0,001 %, is given. Information on the construction of the machine is also given, as are details of the control system. The results of comparison tests between the machine and NPL’s other deadweight machines, carried out as part of the commissioning procedure, are described. The conclusion is made that the machine will be suitable to act as the pilot machine in a forthcoming CIPM 100 kN Key Comparison.