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...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
In many circumstances some one may be compelled to use a force transducer under loads less than 10% of its capacity. It is so important to know the metrological characteristics of the force transducers at this small range in order to be aware how much these characteristics are poor under this force range. Two different types of class 00 force transducers are used. For each type different transducer capacities are considered. The force transducers are calibrated according to ISO 376 in compression within two ranges. These ranges are 10% and 100% of the transducer capacity. The transducer...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
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....
Force, Mass and Torque Measurements · TC3 · 2005 · Download
Because it is still defined in terms of an artefact, the limit on the accuracy with which the SI unit of mass can be realised is largely limited by the surface stability of the kilogram standard. Not only is this true on the case of the International Prototype used to define the unit but also for national standard copies and indeed for mass standards in general. This paper describes the use of x-ray photoelectron spectroscopy (XPS) to study the accretion of contamination of the surfaces of standard masses. Angle resolved X-ray photoelectron spectroscopy (AR XPS) was used to characterise the...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
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...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
This paper describes a new method to evaluate a force standard machine by using a build-up system. The sum of three force signals from three force transducers in a build-up system can be used as a reference value for an intercomparison of force standard machines. At the same time, the small amount of differences between force signals from the build-up system can be used to estimate side force components of a force standard machine. This paper explains theoretical derivation and assumptions of the method. One example of using the method is included in this paper. A 500 kN deadweight force...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
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...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
The pressure balance is very widely used in pressure metrology. The instrument’s operating principle requires that different mass combinations be loaded on a piston to set different pressures. An automated mass handling system for an existing line of high performance pressure balances has been introduced. The new system is a simple accessory that automates mass handling in both gauge and absolute measurement modes with mass sets up to 100 kg. When combined with existing automated pressure control, automated mass handling makes fully automated operation of pressure balances possible....
Force, Mass and Torque Measurements · TC3 · 2005 · Download
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...
Force, Mass and Torque Measurements · TC3 · 2005 · Download
At IMEKO - XV World Congress, the design of the first UK national torque calibration machine was described. Following the construction of the machine, this paper describes its commissioning, leading to the establishment of the first UK national static torque calibration standard. The novel vertical transducer orientation is made possible through several innovative sub-assemblies. This paper evaluates the performances of these critical sub-assemblies, and compares them against design specifications.
Force, Mass and Torque Measurements · TC3 · 2005 · Download