IMEKO Event Proceedings

Page 10 of 770 Results 91 - 100 of 7695

Francesco Orsini, Andrea Rossi, Andrea Scorza, Fabio Botta, Salvatore Andrea Sciuto
A comparison between a commercial WBV platform and an experimental prototype

There are many commercial WBV platforms for clinical applications but in literature very few have been tested to verify their actual amplitude, frequency spectra and waveform shape of vibration, although some clinical studies showed that these parameters can influence significantly the muscles performance. In this study the performances of a prototype WBV1 designed by the authors are compared with a commercial platform WBV2 typically used in clinical and rehabilitation investigations. Tests performed with four accelerometers in 3 different directions show the presence of transversal accelerations that in some cases exceeded the vertical one in WBV2 while they were always lower than the 25% in WBV1. Also the waveform shape of the vibration provided by WBV1 , evaluated by means of the SINAD parameter, show a better value compared to the commercial device: indeed secondary harmonics reaches the 30% of the fundamental in WBV2 but they are always below the 25% in the prototype.

Xumo Li
A COMPARISON BETWEEN A RESISTANCE BRIDGE AND AN INTEGRATED-CIRCUIT RESISTANCE THERMOMETER READOUT USED FOR SPRT CALIBRATION

Specially designed bridges are used for standard platinum resistance thermometer (SPRT) calibration to achieve lowest uncertainty. Such bridges are expensive and their measuring speeds are slow. A new type of instrument reported a few years ago was compared against the bridge to see if it is possible to use the new instrument instead of the bridge for SPRT calibration in some cases. Four SPRTs were calibrated at the triple point of water and the freezing points of tin and zinc using a Model 6010T Bridge and the new instrument (Model 1590) simultaneously. At these calibration points the maximum differences between the two instruments were within 0.4 mK at the tin point, and within 0.7 mK at the zinc point. The maximum difference in resistance ratio W(t) at these points was within 0.9 ppm of the readings. The differences over the entire range from 0°C to 419.527°C were calculated for the four SPRTs. The maximum differences were within 0.1 mK close to 0°C, within 0.5 mK at 300°C and within 0.7 mK at 420°C. The comparison results show the new instrument can be used for SPRT calibration to achieve an expanded uncertainty (k = 2) as low as 1.5 mK.

Barry Pratt, Andy Robinson
A COMPARISON BETWEEN SUPPORTED AND UNSUPPORTED BEAMS FOR USE IN STATIC TORQUE CALIBRATIONS

In industry, calibration beams are frequently coupled directly to the measurement transducer. This paper aims to quantify the effect of using such a method in contrast to the bearing supported case for a range of commercially available transducers.

Michal Ulvr, Petr Kašpar
A COMPARISON OF DC AND AC METHODS FOR CALIBRATION OF SEARCH COILS WITH A HIGH AREA TURNS VALUE

Search coils are widely used for measuring AC magnetic fields, and in special cases for measuring DC magnetic fields with the webermeter and for comparing magnetic flux density standards and magnetic flux standards. This paper compares the measuring equipment that is used and the accuracy that can be achieved by known DC and AC methods for calibrating search coils with a high area turns value.

S. Davidson
A comparison of primary platinum-iridium kilogram mass standards among eighteen European NMIs

The kilogram is unique among the base SI units in being the only one defined by an artefact rather than with relation to naturally occurring physical constants. A major problem with maintaining the traceability of the mass scale is the inherent instability of the kilogram artefacts. National standard kilograms accrete surface contamination over time which leads to an increase in their mass values. Without reference to the international prototype kilogram it is difficult to assess the magnitude of this mass gain and the traceability of measurements is compromised to some extent. This comparison examined the values of the national standard kilogram of 18 European NMIs, each of which uses an algorithm to predict the mass gain of their national standard. The results have been used to evaluate the accuracy of these algorithms and also to recommend a best-fit algorithm for the modelling of mass gain of national standard kilograms.

S. Nattapon, S. Tassanai
A COMPARISON OF PURELY STATIC AND CONTINUOUS TORQUE CALIBRATION PROCEDURE

This paper presents the results of calibration procedure comparison in pure torque measurement with a synchronous system between the purely static (step-by-step) and continuous (quasi-static) facilities in order to prove the influence of the procedural conditions on the uncertainty of calibration. The filter setting (Low pass Bessel: 0.2 Hz, 1.25 Hz, 5 Hz and 10 Hz) and speed of applying torque (≈ 0.7 % of full scale/sec to ≈ 2.8% of full scale/sec) were varied to examine the effects of both parameters on the measurement results and to optimize the continuous procedure. The measurement was made by a torque calibration machine (TCM) with a reference torque transducer and the HBM MGCplus amplifier system using a comparison method.
The results of this experiment show the deviation between the purely static and continuous procedure within ± 0.01% of reading that was enough for class 0.2 torque measuring devices (DIN 51309) and torque transfer wrench (DAkkS-DKD-R 3-7) calibration. For the step-by-step measurement, the duration time in each torque step (form applying torque to data record) must be adequate for steady state of filter setting. For the continuous measurement, the speed of applying torque and filter setting should be optimized for best measurement capability.

Daniela Ichim, Franco Pavese
A COMPARISON OF THE INITIAL UNCERTAINTY BUDGET AND AN ESTIMATE OF THE POSTERIOR UNCERTAINTIES, IN THE CASE OF LARGE BATCHES OF CALIBRATION DATA: THE LHC THERMOMETERS AT CERN

The paper will describe the techniques that have been used to perform the comparison on large batches of cryogenic semiconductor-type thermometers, calibrated for the CERN LHC and the main results obtained: they concern either the uncertainty of the CernoxTM thermometers under calibration and the behaviour of the standards used during the calibrations.

J. Jokela, F. Pollinger, N. R. Doloca, K. Meiners-Hagen
A COMPARISON OF TWO WEATHER DATA ACQUISITION METHODS FOR THE CALIBRATION OF THE PTB GEODETIC BASELINE

The Physikalisch-Technische Bundesanstalt has recently refurbished its geodetic baseline in Braunschweig, Germany, and the baseline is now supplied with an inclusive set of environmental sensors for weather observations. The Finnish Geodetic Institute calibrated the baseline in June 2011. In the calibration, the observers also used conventional instruments, common in surveying work, to obtain weather data. By comparing the two weather data sets and the results computed when using them, it is possible to demonstrate the good capability of conventional instruments, when properly used. The results of the comparison, which are applicable in electronic distance measurements for conventional surveying, are presented in this paper.

Ercihan Kiraci, Glen A Turley, Alex Attridge, Alan Olifent, Mark A Williams
A COMPARISON STUDY OF ON-CMM LASER SCANER AND TOUCH TRIGGER PROBE FOR AUTOMOTIVE MEASUREMENT APLICATIONS

Coordinate Measuring Machines (CMMs) are considered as the most accurate metrology equipment and are used widely in the manufacturing sector. Traditionally, touch trigger probes have been employed but more recently non-contact laser scanning sensors have been developed, offering potential advantages in terms of speed and number of points captured. Laser scanning is attracting significant interest from industry due to its ability to characterise complex, free-form surface geometries which are becoming common in the styling of automotive body panels. However, laser scanning sensors do not currently offer the accuracy and repeatability that can be achieved with touch trigger probes. Furthermore, there are no recognised standards for qualifying non-contact probes, making reliable verification of measurements difficult to achieve. Past research has attempted to qualify the capability of different non-contact probing technologies using small artefacts designed for technology validation; however, little work has been done on the verification of on-CMM laser scanning technologies for large volume, industry-relevant measurement applications. This study used a full-scale machined physical representation of a sheet metal vehicle body to evaluate the measurement agreement and repeatability of a laser scanning sensor, relative to touch trigger probe measurements, mounted on a horizontal arm CMM using individual surface points, edge points and circular holes, located across the entire structure. Through the use of a static repeatability analysis it was found that there was good correlation between touch trigger probe and laser scanner measurements. Repeatability of the laser scanner was found to be better than 28 µm for surface, edge and circular holes measurement. Accuracy of the laser scanner relative to the touch trigger probe measurements fell within a range of 50 µm which is a factor of 10 lower than typical automotive body-shell manufacturing tolerances. The results collected demonstrate that laser scanning sensor and CMM used in this study would provide a level of accuracy and repeatability better than which is typically required by automotive manufacturers for body-in-white quality inspection applications.

Ireneusz Jablonski, Adam G. Polak, Janusz Mroczka
A COMPLEX MATHEMATICAL MODEL OF THE RESPIRATORY SYSTEM AS A TOOL FOR THE METROLOGICAL ANALYSIS OF THE INTERRUPTER TECHNIQUE

The paper presents the issue connected with the construction and simulations of the complex mathematical model of the respiratory system for the interrupter technique. Combining morphometric data for the consecutive segments of the object (assumption on symmetrical structure of the bronchial tree) with information on existence and proportions between the processes, proper for the interrupter experiment, resulted in an exact imitation of the occlusion conditions, both in the time and frequency domain. It is expected that the model will be a base for design of the simple and reliable diagnostic test dedicated to the respiratory mechanics measurement. From this point of view, the proposed complex mathematical analog of the respiratory system during airflow interruption is a forward model in the forward-inverse scheme of cognition.

Page 10 of 770 Results 91 - 100 of 7695