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Page 855 of 977 Results 8541 - 8550 of 9762

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.

M. Grum, M. Terlep, M. Oblak, L. Miklavcic
THE DETERMINATION OF GRAVITY ZONE FOR WEIGHING INSTRUMENTS IN SLOVENIA

Several derivations from the WELMEC gravity concept concerning non-automatic weighing instruments that are sensitive to the gravity were developed and analyzed. Apart from that, the gravity field model was developed for a territory of the Republic of Slovenia based on the geographical data and empirical gravity formula. It was established that some simplifications comparing to the WELMEC gravity zone concept could be introduced regarding free movement of weighing instruments across Slovenia. Limitations were set up concerning instruments’ characteristics that have to be regarded when the simplifications are used.

M. Oblak, M. Grum, M. Terlep
MAGNETIC PROPERTIES OF OIML SHAPED WEIGHTS

The work presents an improved approach to the determination of magnetic properties of weights, which have a shape according to OIML R111. The main stress is laid on a measurement of the volume magnetic susceptibility and an evaluation of its uncertainty. The method is presented, how the volume magnetic susceptibility of the OIML weight can be determined taking into account an actual shape of the weight instead of using only an approximation of its shape with "outer" and "inner" cylinders. Monte Carlo simulation was used to evaluate the measurement uncertainty. The susceptibility of 1 kg weight was calculated by the method of "outer" and "inner" cylinders and the method presented in the article. Results of both methods are compared and discussed.

Adrian Gherasimov, Eugen Ghita
THE TRACEABILITY SYSTEM OF FORCE MEASUREMENTS IN ROMANIA

The paper presents some technical aspects about the Romanian system built-up to ensure the traceability of force measurements to the SI units. The regulations of the traceability schemes and the steps to be followed are presented. The Force Laboratory Timisoara, pending of Romanian Bureau of Legal Metrology proposed and implemented the national traceability of force measurements. The paper presents the best measurements capabilities, which the Romanian calibration laboratories offer for force measurements. In order to perform a national and international validation of the force measurements in Romania, the traceability system must be in accordance with the national and international standards. One of the major parameters of the traceability system is the uncertainty associated with calibration or measurement results. This trend is based on the explosive implementation of the ISO 9000 series and ISO 17025 requirements in industry and other fields. The Romanian Government putted forward some regulations in order to provide for the necessary conditions to report the results to the acknowledged standards.

Adrian Gherasimov, Eugen Ghita
THE UNCERTAINTY OF MEASUREMENT IN CALIBRATION USING A COMPARISON FORCE STANDARD MACHINE

The paper presents a practical example for the evaluation of the uncertainty in calibration using a comparison force standard machine with a maximum load of 1000 kN, tension and compression mode. The uncertainty of measurement associated with the input estimates is evaluated. It is also presented a way to minimize the uncertainty of the applied force with the view to attaining the necessary value for the calibration of class 1 force transducers, in accordance with ISO 376:1999. For this purpose an evaluation of the loading regime of the force machine is presented. There was identified the main input components influencing the uncertainty in calibrations, such as the force stability during measurements and the metrological characteristics of the reference transducers. Further are presented the practical results of the investigation of the force comparison machine after the optimization, including the technical and economical benefits.

Page 855 of 977 Results 8541 - 8550 of 9762