89 research outputs found

    Application of Statistical Tools to Optimize a Dual Source Electrical High Dc Resistance Bridge

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    At the Istituto Nazionale di Ricerca Metrologica (INRIM), a commercial dual source high resistance bridge has been optimized by means of the application of statistical tools and of the analysis of measurements distributions. These tools help to achieve the best precision for resistance ratio measurements in the range 10 T & OHM; & DIVIDE; 100 T & OHM;. A measurement procedure consisting of multiple steps, in which at each one the value of the resistor under calibration is updated and has been considered the best one. With this procedure, at the third step, the lowest standard deviation of the mean and the measurements distribution approximately normal are obtained regardless of the settle time, of the resistance ratio, of the measurement voltages and of the resistors under comparison. This comes from the achievement of the white noise regime and from a bridge balance close to the ideal. This measurement procedure therefore allows also to achieve the lowest measurement uncertainty due to the minimization of the type A uncertainty. The Allan variance and the power spectral density were used to identify the white noise analyzing the detector readings. Strict triangulation rules were also established and applied to validate both the measurement process and the chosen model to extrapolate the values of the standard resistors at low voltages

    Evaluation of the measurement capabilities of an high performance commercial high resistance bridge by means of the comparison with two validated high resistance measurement methods

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    À l'Institut national de la métrologie de recherche (INRIM) ont réalisée une comparaison de mesure entre un pont de mesure de haute résistance électrique commerciale et deux méthodes de mesure de haute résistance électrique validés utilisé à l’INRIM. Ils ont procédé à une estimation de l'incertitude de mesure du pont à partir de 10 G jusqu'à 10 T. Quatre étalons de haute résistance de haut niveau à partir de 10 G jusqu'à 10 T ont été calibrés avec les trois méthodes de mesure. La compatibilité de ces mesures était bon. Quelques problèmes pour les mesures plus de 10 T et dans l'évaluation de l'incertitude de mesures du pont, cependant, restent en suspens

    High accuracy transportable selectable-Value High Dc Voltage Standard

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    À l'Institut national de recherche metrologique (INRIM) il a été développé un étalon de haute tension continue avec des valeurs sélectionnables de 10 V à 100 V pour compenser le manque d'étalons de haut niveau de tension continue d'une valeur supérieure à 10 V pour les comparaisons interlaboratoires de haut niveau. Il a été utilisé une nouvelle technique électronique de terre mobile. L'étalon développé a un bruit inférieur et il a la stabilité égal à celle des calibrateurs de tension continue ou multifonction de haut niveau largement utilisé dans les laboratoires d'étalonnage électriques; il a aussi une meilleure attitude à être transporté pour les comparaisons interlaboratoires. Le projet est extensible jusqu'à 1000 V

    Towards a traceable divider for composite voltage waveforms below 1 kV

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    open3Voltage divider ¬∑ Composite and combined voltages ¬∑ Traceability ¬∑ Scale factor calibration ¬∑ Step response ¬∑ Measurement uncertaintyIn the framework of the European Project 19NRM07 HV-com2 supporting the standardization in high-voltage testing with composite and combined wave shapes, a divider to employ in a test set-up for validation of electrical devices submitted to composite voltages below 1 kV has been developed at the Istituto Nazionale di Ricerca Metrologica (INRIM) and currently is under extensive testing. After a simulation stage, an available divider has been modified to comply with the IEC 60,060 requirements in terms of step response and scale factor. To be suitably fast in replying to step voltages, an adjustment of the components of the low-voltage arm has been made. The divider has been calibrated with traceability to the relevant INRIM National Standards and characterized exploiting its scale factor at different voltages and frequencies. The divider has been then inserted in a set-up with a sinusoidal generator, an impulse generator and coupling‚Äďblocking elements to carry out tests at low voltages (below 1 kV) with single voltages. In these tests, the divider showed a satisfactory attitude as converting device and its scale factor is traceable with suitable uncertaintyopenGalliana, F.; Caria, S. E.; Roccato, P. E.Galliana, F.; Caria, S. E.; Roccato, P. E

    The Effect of Thermal Stresses on the Electrical Resistance of Crimped Connections

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    Cables headed with crimped lugs are frequently used in test laboratories in temperature rise tests carried out to validate electrical devices. The increase in the electrical resistance of the crimped connections can cause high dissipation of power and heat during these tests, impairing their outcome. This work evaluates the effect of thermal stresses on the resistance and on the dissipated power of crimped connections. This resistance was found to be more sensitive to thermal stresses than to mechanical ones analysed in a previous work. A limit of the dissipated power from crimped connections during temperature rise tests was estimated to be about 4 W corresponding to a crimp resistance of 24 mu ohm for tests made at 400 A. Respecting these limits could avoid unnecessary rejections of equipment under test
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