This article is concerned with the use of counterrotating mechanical bearings in torque calibration sys- tems. First a short overview on some general aspects of this bearing type will be given, which includes a general description of their construction as well as of their functionality. The main section deals with experimental examinations made on the performance of counterrotating bearings. These experiments were completed mainly using the horizontally arranged MIKES-RAUTE 2 kN·m torque standard calibra- tion device. Additionally initial results gained with the new vertically arranged 20 kN·m torque reference device are included. Main points of interest were the particular elements of the uncertainty budget as stated in EA-10/14. They are opposed for counterrotating and standing bearings. Also some investiga- tions about other error influences of the bearings are presented. Overall these results show that counterro- tated bearings can provide a strong reduction of uncertainty but also need some further investigation es- pecially in vertical devices.

For the determination of the local gravity high precise mobile gravimeters are in use since more than a hundred years. As a result of the basic measurement principle the determination is carried out point-by-point with the consequence that the procedure is time consuming and expensive. Thus in many countries the results of several measurement campaigns have been collected over decades. Whereas the measured values are available to the public only to some extent, the data were of- ten processed to gravity anomaly maps for the purpose of geological ground surveys. In this research two samples of gravity anomaly maps of Northern Germany and Italy are intro- duced with a detailed description of the rebuild of a gravity value from an anomaly map. For the single steps a theoretical budget of the uncertainty is given which has been verified by inde- pendent control points.

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.