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Page 699 of 977 Results 6981 - 6990 of 9762

M. Danaci, S. Sagiroglu
A NEURAL SYSTEM FOR AN AUTOMATIC WEIGHING

Multilayered perceptron neural networks are employed to model a weighing system to estimate the applied mass accurately while the system is still in the transient mode. This is achieved through the networks trained with the backpropagation and the extended delta-bar-delta algorithms to compare the performance of the networks. The results obtained from neural models show that the both neural models are found successful especially if the data sets are noisy.

Ü. Y. Akçadag, S. E. San
NEWLY ESTABLISHED HYDROMETER CALIBRATION SET UP AT UME

Hydrometer calibration could be performed by "Cuckow Method" in which just a single liquid is sufficient for the calibration of the whole scale. Hydrometers are weighed first in air and then in a reference liquid in this method. The density of the reference liquid is well known and it is possible to determine the associated density value of the graduation mark by making use of weighing values and the density value of liquid in related formulas. The entire scale of Hydrometer can be calibrated in this way by immersing the hydrometer to the interested scale marks. In this paper, hydrometer calibration set up of UME is introduced and obtained measurement results from this set up are given for a sample hydrometer.

M. Danaci
NEW APPROACHES FOR HIGH SPEED AND ACCURATE WEIGHT MEASUREMENTS

Accurate and fast weighing is an important requirement throughout the modern world. The application of an object to a weighing platform results in a transient output waveform, which can take a considerable time to settle sufficiently before the object can be accurately measured or predicted. In this study, an improved method is investigated based on the Gauss-Newton method of the Non-Linear Regression (NLR) in which a time-domain model is fitted to displacement data from a weighing platform. The applied mass is accurately predicted in the early part of the transient response for different cases. Simulations confirm that the various modeling, identification and prediction approaches are successful over a wide range of applied masses and noise amplitudes. Comparisons with previously known dynamic weighing methods show signal that significant speed and accuracy advantages can be obtained.

S. Tigrel, S. Kaçmaz, F. Tigrel
PRODUCTION OF ELECTRONIC MASS COMPARATOR WITH LOAD CELL AND CAPACITY OF 1500 KG

An electronic weighing instrument with a capacity of 1500 kg and resolution of 10 g were produced. The balance was designed with three high accuracy load cells and counter weights as 500 kg and 1000 kg. Also counter weights are used as reference standard for mass measurement. Standard deviation, linearity error and eccentricity error were measured for the weighing instrument.

W. G. Lee, Y. J. Lee
AUTOMATIC WEIGHT EXCHANGER FOR SERIES DESIGN CALIBRATION

An automatic weight exchanger for series design calibration of a decade weights is described. The vertical pan with 6 loading positions is hanged down from a balance hook. Weights are loaded on and lifted off vertically. Every weight has its own vertical guide for lifting and loading. The vertical motion is realized by 6 synchronous stepping motors. The weight exchanger is installed with a commercial balance of 205 g capacity and 0.01 mg readability. The full operation is automated with a personal computer. The performance tests were carried out. The present status results indicate: Calibration time and labor could be reduced significantly. Uncertainty could be reduced by reducing operator’s random error. Calibration series of 100-50-20-20’-10-10’ g was tested successfully to give maximum Type A uncertainty of 0.014 mg. The apparatus will be incorporated with Internet web for remote calibration and education.

W. Beer, A. L. Eichenberger, B. Jeanneret, B. Jeckelmann, A. R. Pourzand, P. Richard, H. Schneiter, J. Schwarz
THE SWISS WATT BALANCE: FIRST MEASUREMENTS

The Swiss Watt Balance is a new type of moving-coil experiment with a very compact design. The aim of the experiment is to link the unit of mass to fundamental constants with a view to a future redefinition of the kilogram. That means to express the kilogram in terms of the meter, the second and the Planck's constant, by equating electrical and mechanical power, with a relative uncertainty of ≤ 10–8. The main features of the Swiss design are a very compact construction and a strict separation between the moving and weighing parts of the experiment. In order to optimize all the key components of the set-up, they were separately tested and accurately characterized. An update on the optical velocity measurement and regulation system, on the permanent magnet and coil assembly assessment, and on the automation of the programmable Josephson voltage standard is given first. In addition, the mass comparator, the characterization of the 100 g gold mass standards, and the absolute gravity measurements are presented. In a second part, the description of a complete sequence of data acquisition is explained in details.

Z. J. Jabbour, R. S. Davis
EFFECTS OF CLEANING ON THE US PROTOTYPE KILOGRAMS

This paper discusses the stability of national prototype kilograms No. 4 and No. 20, belonging to the United States. Calibration history, changes in mass with respect to time, and effects on mass and surface profiles due to cleaning and washing are described.

K. Riski, A. Oja, T. Sillanpää, H. Sipola, H. Seppä, J. Kiihamäki, P. Seppälä, J. Karttunen
MICROMECHANICAL SILICON MICROBALANCE

A micromachined capacitive silicon microbalance has been designed and fabricated. It is intended for weighing masses of the order of 1 g with a resolution and accuracy of about 1 µg. The device consists of a micromachined SOI (silicon-on-insulator) chip which is anodically bonded to a glass plate. The capacitance is formed between two electrodes. The flexible electrode is the SOI layer. The other electrode is metal layer on the glass. The glass electrode is divided into three sections. The sections are used for detecting the tilting of the top electrode due to eccentric loading. The measuring circuit implements electrostatic force feedback which keeps the top electrode at a constant horizontal position irrespective of the mass of the load. First test measurements have demonstrated that an accuracy of about 2 to 3 µg at 1 g can be reached.

K. Riski, P. Heikkinen, H. Kajastie, J. Manninen, H. Rossi, K. Nummila, E. Frantsuz, V. Khavinson
DESIGN OF A SUPERCONDUCTING MAGNETIC LEVITATION SYSTEM

A preliminary project for the realisation of the kilogram using the "superconducting magnetic levitation method" has been started at MIKES. The work will be carried out in co-operation with VNIIM, Russia. In the levitation method there are still problems, which have to be solved before the final goal, a relative uncertainty of 10-8 for the kilogram, can be reached. The main problem at present is energy losses due the incompleteness of the Meissner effect. These losses will be generated if the magnetic flux intrudes into a superconductor. Energy losses can jeopardise the experiment. To measure these losses we are developing a cryogenic calorimeter. The resolution of the device will be about 1 nW. We have also started to optimise the geometry of the levitated body and the coil, which produces the levitating magnetic field in order to minimise the effect of the energy losses.

J.W. Chung, K. S. Ryu, R. S. Davis
CONSIDERATIONS REGARDING THE MAGNET USED IN THE BIPM SUSCEPTOMETER

A susceptometer developed at the Bureau International des Poids et Mesures is used by many national laboratories to determine the magnetic properties of stainless-steel mass standards. This device relies on a small, cylindrical magnet to simulate a magnetic point dipole. According to simple theoretical considerations, a) the magnetic moment of the cylindrical magnet which is used can be determined by the susceptometer itself, b) the uncertainty in the magnetic moment contributes weakly to the combined uncertainty of any measured susceptibility provided that unknowns are measured relative to a standard of similar size, and c) a cylindrical magnet whose ratio of height/diameter is 0.87 best approximates a point dipole. Experimental tests of these assertions will be presented.

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