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Page 897 of 939 Results 8961 - 8970 of 9382

Antti Lassila, Jorma Jokela, Markku Poutanen, Xu Jie
ABSOLUTE CALIBRATION OF QUARTZ BARS OF VÄISÄLÄ INTERFEROMETER BY WHITE LIGHT GAUGE BLOCK INTERFEROMETER

Measurement of a baseline with Väisälä interferometer is a traditional high accuracy length measurement in geodesy. An accurate length up to 1 km is achievable by interferometrically multiplying the length of a 1 m quartz bar. Therefore, the absolute length of the bar should be known with small uncertainty. A measurement setup and procedure for calibration of length of a quartz bar by combined white and laser light gauge block interferometer has been developed. The calibration procedure, results and uncertainty evaluation are presented. A standard uncertainty of 35 nm has been achieved.

Lifong Zou, Dayananda Samarawickrama, Kevin Seymour, Ken Stout
FREE FORM SURFACE MEASUREMENT USING NON-CONTACT MEASUREMENT METHODOLOGY

Quality control is applied to almost every procedure during the manufacturing process in industry. However, it is not used commonly in restorative dental practice. The surface contour or shape of the tooth is very irregular, a 'so called' free form surface. Measurement of such a free form surface needs a specified strategy to satisfy the measurement accuracy. This paper attempts to propose an optimal measurement strategy to measure the occlusal molar tooth surface, in order to achieve a degree of measurement and quality control in restorative dental practice.

Tanfer Yandayan
LARGE MEASUREMENT RANGE MECHANICAL COMPARATOR FOR CALIBRATION OF LONG GAUGE BLOCKS

A new design of mechanical gauge block comparator for calibration of long gauge blocks is described. The comparator is constructed by modification of a commercially available universal length measuring machine. It is able to compare the different nominal size gauge blocks with its 300 mm measurement range. This has the advantage that a reference metric size gauge block can be used to calibrate the inch size square or rectangular section gauge blocks or vice-versa. Line scale of the length-measuring machine, which is calibrated by a laser interferometer and gauge blocks, is used for the measurement of displacement. Calibration procedure adapted from EAL-G21 guideline is described with the aid of the results. The uncertainty of the measurements is evaluated and the parameters, which has influence on the uncertainty, is described in detail. The successful application of the comparator for calibration of metric or inch gauge blocks in different cross sections up to 500 mm or 20 inch nominal size is presented with the results. The uncertainty of the comparator with k = 2 is U = [ 1502 + 0.5 L)²]1/2 nm, where L is the gauge block length in mm. For instance, U is calculated as 292 nm (k = 2) for 500 mm long gauge block.

Sarwat Zahwi, Monier Koura, Alia Mekawi
FACTORS INFLUENCING UNCERTAINTY EVALUATION FOR SURFACE ROUGHNESS MEASUREMENTS

The nominal conditions for measuring surface roughness when using stylus instruments are specified in ISO 3274. Deviations from these nominal conditions lead to significant deviations of the measured roughness parameters. An uncertainty evaluation has been made on five roughness parameters for three calibration standards. The methods and procedures for uncertainty evaluation are to i) calibrate and evaluate the uncertainty in the condition for the measuring instrument, ii) evaluate the influence of each individual deviation on the results of measurement, and iii) combine the effect of these individual uncertainties on the final result of measurement. A study has been carried out on the influence of different contributors on the combined uncertainty associated with the assessment of roughness parameters. From the results the major contributors affecting the uncertainty of measurement on different roughness parameters are given.

A. Titov, I. Malinovsky, C.A. Massone
NANOMETROLOGY REGIME IN LENGTH MEASUREMENTS OF MATERIAL ARTEFACTS WITH NOMINAL LENGTHS UP TO 100 mm

New calibrated double-sided method of interferometric length measurements with quartz reference plate is reported. The method is free from wringing errors, and can be used for the improvement of measurements of material artefacts. Limitations of the interferometric measurements are discussed. Some systematic errors are measured with a sub-nanometer resolution.

K. Umetsu, R. Furutani, T. Takatsuji, S. Osawa, T. Kurosawa
CALIBRATION OF A CMM USING A LASER TRACKING SYSTEM

A new calibration approach of a coordinate measuring machine (CMM) using a laser tracking system is proposed. According to the conventional approach of the laser tracking system, trilateration principle is mainly adapted. Therefore one retroreflector and four laser trackers are required. Though this approach is capable of attaining high accuracy measurement, measuring volume is likely to become smaller due to physical limitations for middle size CMM. Consequentially, we need new approach, which uses the least laser trackers in numbers. In this paper, effective calibration strategy to estimate 21 kinematic parameters of CMM’s axes is described. Additionally to confirm the validity of the proposed approach, the parameters estimation using a ball plate was conducted in parallel. The estimation results by the laser tracker and the ball plate showed good agreement.

Ch. Papageorgiou, Th. Laopoulos
ACCURATE DISPLACEMENT MEASUREMENT BASED ON THE FREQUENCY VARIATION MONITORING OF ULTRASONIC SIGNALS

This paper introduces a different approach to the measurement of the time-of-flight of ultrasonic signals. Frequency variation monitoring and recording is used to determine accurately the arrival time of the ultrasonic signal. A high speed Digital Signal Processor (D.S.P.) is used for both: transmission and direct measurement of the frequency of the incoming signal in every single period and with an accuracy of about 0.1%. The proposed configuration offers small size and low cost solution to displacement measurements with a remarkable performance in terms of accuracy, range and measurement time.

José Sánchez, Saúl Santillán, Sergio Padilla, Benjamín Valera, Rigoberto Nava, Gerardo Ruiz
VIRTUAL INSTRUMENTATION, OVERCOMING NON-LINEARITIES WHEN ERRORS OF MULTIAXIS MACHINES ARE AMPLIFIED

Abstract - One purpose of Virtual Instrumentation in Metrology, is to empathise properties that put instrumentation away from idealisations. In actual instrumentation, geometric deviations trend to occur in relations 10-5, 10-7 of maximum displacements, requiring their representation in amplified way. If distortion of mechanisms is amplified hundreds times for its representation in CAD, many problems occur: linearity is lost between geometric relations; it is difficult to represent errors simultaneously for many axis and many degrees of freedom; operation of mechanisms doesn't satisfy cinematic of rigid body.
Since linearity is lost between linear and angular displacements, between articulate and operational spaces, and between real and amplified representation, it is necessary to apply functions and mapping procedures for relating them. Those mapping errors and their functions are important goals in the field of calibration, where virtual mechanical instrumentation may illuminate cases of controversy. The manuscript treats with several cases of distortion, their possibilities of amplification, their possibilities of assembling, and diagnostic trough inverse kinematics.

Ken Shimojima, Ryoshu Furutani, Kiyoshi Takamasu, Kenji Araki
THE ESTIMATION METHOD OF UNCERTIANTY OF ARTICULATED COORDINATE MEASURING MACHINE

Articulated Coordinate Measuring Machines (A-CMM) are commercial products. However, it is difficult to keep the traceablity of it, because the calibration of A-CMM is performed by the manufacturer’s own method. We planed to use 3D artifact, which had 9 balls for calibration, and test it. The kinematical model of A-CMM was described in D-H notation. In A-CMM measurement, a cone-shaped stylus was used. We measured the artifact in five different locations and orientations. Because the artifact has nine balls, 45 points in total ware measured. the parameters were determined in each location and orientation. Each set of kinematical parameters is applied to the measured points in five different locations and orientations. Then the root mean squares are calculated in 25 kinds of combinations. As a result, the calibration result is better than the specified accuracy of Vectron.

Atsushi Taguchi, Takashi Miyoshi, Yasuhiro Takaya, Satoru Takahashi
HIGH PRECISION INSTRUMENT FOR MICRO SURFACE PROFILE MEASUREMENT BASED ON OPTICAL INVERSE SCATTERING PHASE METHOD

With the advance of microtechnology, inprocess or in situ measurement techniques for measuring surface profiles of engineered micro parts have been increasingly required. We have proposed an optical measurement technique, the optical inverse scattering phase method, which can be applied to the in-process measurement of micro-surface profile with the accuracy in the nanometer order. An instrument has been designed and developed on the basis of the proposed principles, and verified by measuring an ultra precision grid plate having rectangular pockets 44nm deep at intervals of 10µm. The measured surface profile gave good agreement with the nominal dimensions of the specimen as well as the one obtained by AFM.

Page 897 of 939 Results 8961 - 8970 of 9382