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Page 814 of 936 Results 8131 - 8140 of 9356

Y.K.Park, R.Kumme, J.T.Lee, W.Herte, H.K.Song, D.I.Kang
ESTABLISHMENT OF FORCE STANDARDS IN KOREA UP TO 2 MN BY HYDRAULIC FORCE STANDARD MACHINE

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.

Martin Girard, Pierre Delajoud
AUTOMATED MASS HANDLING FOR HIGH PERFORMANCE PRESSURE BALANCES

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. Automation of mass handling and pressure balance operation brings both practical and metrological benefits to pressure metrology.

Andy Knott
DESIGN, DEVELOPMENT, AND COMMISSIONING OF A 120 kN DEADWEIGHT FORCE STANDARD MACHINE

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.

Andy Robinson
THE COMMISSIONING OF THE FIRST UK NATIONAL STANDARD STATIC TORQUE CALIBRATION MACHINE

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.

Thomas Fehling, Thomas Fröhlich, Detlef Heydenbluth
THE NEW SARTORIUS 1KG-PROTOTYPE BALANCE FOR HIGH PRECISION MASS DETERMINATION

The 1kg-prototype balance is a result of the technical collaboration between the Sartorius AG and the BIPM. Construction and functionality of the 8-position load alternator are based on the known BIPM FB2-technology. The 1kg-Prototype balance is constructed for highly accurate mass determination and is developed to create and maintain the national mass scale as well as the use for research and development. It permits the weighing of Pt-Ir or stainless steel masses from 100g to 1 kg as well as 1kg silicon spheres or buoyancy artifacts. The complete measurement device is installed inside an enclosed airtight aluminum chamber which can be evacuated to primary vacuum. The load alternator can be loaded comfortably through a quick load-lock device. Additional standard vacuum flanges are freely available for measuring sensors, control purposes and electronic or other connectors. The control unit running the control software allows flexible and easy programming of the required measuring sequences. Routine matter mass calibration as well as complex weighing series could be done. A detailed description of the technical and metrological parameters and possible applications are given. The function of the load alternator and the load-lock device is depicted.

Jong-Ho Kim, Hyo-Jik Lee, Jeong-Il Lee, Yon-Kyu Park, Min-Seok Kim, Dae-Im Kang
FABRICATION OF A THREE-COMPONENT FORCE SENSOR USING MICROFABRICATION TECHNOLOGY AND ITS EVALUATION

This paper describes the development of a three-component silicon-based force sensor with a square membrane using bulk micromachining process. The designed sensor, with size of 2 mm x 2 mm, has a maximum force range of 5 N in the x, y, and z direction. Optimal locations of piezoresistors were determined by the strain distribution obtained from finite element analysis and beam theory. Finally three Wheatstone bridge circuits were arranged and verified under Fx, Fy, and Fz loading conditions. The silicon-based sensor was fabricated using bulk microfabrication technology(MEMS). The piezoresistors for measuring the change of resistance, like strain gage, were embedded in silicon wafer (Si) using ion- implantation diffusion technique. An epoxy mesa(SU-8) is built-up on top of the silicon to convert an applied force to a distributed stress. Finally, the membrane of the sensor was fabricated by using bulk- micromachining process based on the anisotropic etching of the silicon. The ability of the sensor to measure both normal and shear forces is investigated and demonstrated through experimental characterization such as normal and shear sensitivity, repeatability, hysteresis and linearity.

Georg Wegener, Jürgen Andrae
MEASUREMENT UNCERTAINTY OF TORQUE MEASUREMENTS WITH ROTATING TORQUE TRANSDUCERS IN POWER TEST STANDS

The objective of the presented study is to introduce a method for estimating the measurement uncertainty of torque measurements. Unlike the well-known approaches, the uncertainty shall take into account the effects acting during torque measurement in industrial applications like power test stands. These effects include the effects also known from laboratory calibration like hysteresis, linearity or interpolation deviation, repeatability, reproducibility. But special emphasis is put on an estimation of their impact under the conditions in the power test stand. Additionally, further effects are included in the consideration, like temperature effects, the influences of parasitic loads and of rotational speed. The mathematical method for an estimation of the uncertainty is presented, the input quantities are discussed and suggestions are made how the uncertainty can be reduced for given applications.

T. Yan, B. E. Jones, R. T. Rakowski, M. J. Tudor, S. P. Beeby, N. M. White
STIFF TORQUE TRANSDUCER WITH HIGH OVERLOAD CAPABILITY AND DIRECT FREQUENCY OUTPUT

A new torque transducer with high overload capability and direct frequency output is reported. It employs the recently developed metallic triple-beam resonators with thick-film printed lead zirconate titanate (PZT) drive and pickup elements. The new torque transducer has been tested in a torque range of up to 20 Nm, resulting in a strain level of 400 microstrain on the measurement shaft surface and giving a large frequency-change output of 800 Hz. The strain level required by the new torque transducer can be much lower (~100 microstrain) than the level (~1800 microstrain) usually required by conventional metallic resistance-strain-gauge-based torque transducers, thus increasing the transducer overload capability by a large factor. Nevertheless, under such a low strain level, the new torque transducer can still output an adequately large frequency change of 200 Hz for measurement. Having a large overload capability is very important in many torque measurement applications where rapid and large overloads can occur.

In-Mook Choi, Jong-Ho Kim, Hyo-Jik Lee, Min-Seok Kim, Yeon-Kyu Park, Sam-Yong Woo, Dae-Im Kang
DEVELOPMENT OF ELECTROMAGNETIC PROBE FOR MICRO FORCE MEAUSREMNT

Micro/Nano force measurement is becoming more essential in the fields of AFM metrology, biomedical industries, chemical industries, and material science. For the micro/nano force measurement, a cantilever mounted with Ni/Cr conducting wire has been fabricated by MEMS process. The cantilever with high sensitivity can be driven by Lorentz force which is generated by applying current into the wire under uniform magnetic flux. In order to measure micro/nano force precisely, the cantilever is controlled to a null position with the Lorentz force opposing to a vertical input force. The active measurement method by null balance is more accurate and sensitive than passive measurement method using a piezoresistive cantilever. For this measurement, the simple electromagnetic circuit is analyzed and constructed to obtain high magnetic flux density, and a spring constant for high force sensitivity and a resonant frequency for the stable control of the cantilever are analyzed by FEA. After the construction of a system with a displacement sensor and a controller, the basic measurement characteristics such as a resolution, linearity, and repeatability, will be determined by experiment, and the comparison calibration with a commercial cantilever will be carried out. This electromagnetic active probe can be used as a transfer standard for the micro force evaluation and dissemination. It would also be applicable to various researches and industries, such as binding-force measurement between molecules, force lithography, and nanoindentation.

Koji Ohgushi, Takashi Ota, Kazunaga Ueda
UNCERTAINTY EVALUATION OF THE 20 kN·m DEADWEIGHT TORQUE STANDARD MACHINE

A deadweight-type torque standard machine of 20 kN·m rated capacity (20 kN·m-DWTSM) has been designed and developed by the National Metrology Institute of Japan (NMIJ) at the National Institute of Advanced Industrial Science and Technology (AIST). Each uncertainty contribution comes mainly from the performance of each mechanical part of the 20 kN·m-DWTSM. Authors evaluated the uncertainty of the mass of the linkage weights, local acceleration of gravity, influence of air buoyancy on deadweight loading, initial moment-arm length (including CMM measurement and temperature compensation), and sensitivity of the fulcrum. This report deals especially with evaluation of the remaining contributions, namely the influence of arm flexure and reference line variation at the end of the moment-arm on best measurement capability (BMC). Estimation of BMC in the 20 kN·m-DWTSM gave a relative expanded uncertainty of less than 7.0 × 10-5 (k = 2) for the calibration range from 200 N·m to 20 kN·m.

Page 814 of 936 Results 8131 - 8140 of 9356