The new IMGC-02 transportable absolute gravimeter: measurement apparatus and applications in geophysics and volcanology

The research carried out at the Istituto Nazionale di Ricerca Metrologica (formerly Istituto di Metrologia «G. Colonnetti») aiming to develop a transportable ballistic absolute gravimeter ended with a new version of the instrument, called the IMGC-02. It uses laser interferometry to measure the symmetrical free rising and falling motion of a test mass in the gravity field. Providing the same accuracy achieved with previous versions, the instrumental improvements mainly concern size, weight, data processing algorithms and operational simplicity. An uncertainty of 9 μGal (1 μGal=1×10–8 m·s−2) can be achieved within a single observation session, lasting about 12 h, while the time series of several observation sessions show a reproducibility of 4 μGal. At this level, gravity measurements provide useful information in Geophysics and Volcanology. A wide set of dynamic phenomena, i.e. seismicity and volcanic activity, can produce temporal gravity changes, often quite small, with an amplitude ranging from a few to hundreds of microgals. Therefore the IMGC absolute gravimeter has been employed since 1986 in surveying the Italian active volcanoes. A brief history of the gravimeter and the description of the new apparatus, together with the main results of ongoing applications in Geophysics and Volcanology are presented

Self-attraction effect and correction on three absolute gravimeters

The perturbations of the gravitational field due to the mass distribution of an absolute gravimeter have been studied. The so called Self Attraction Effect (SAE) is crucial for the measurement accuracy, especially for the International Comparisons, and for the uncertainty budget evaluation. Three instruments have been analysed: MPG-2, FG5-238 and IMPG-02. The SAE has been calculated using a numerical method based on FEM simulation. The observed effect has been treated as an additional vertical gravity gradient. The correction (SAC) to be applied to the computed g value has been associated with the specific height level, where the measurement result is typically reported. The magnitude of the obtained corrections is of order 1E-8 m/s2.Comment: 14 pages, 8 figures, submitted to Metrologi

The new IMGC-02 transportable absolute gravimeter: measurement apparatus and applications in geophysics and volcanology

The research carried out at the Istituto Nazionale di Ricerca Metrologica (formerly Istituto di Metrologia «G. Colonnetti») aiming to develop a transportable ballistic absolute gravimeter ended with a new version of the instrument, called the IMGC-02. It uses laser interferometry to measure the symmetrical free rising and falling motion of a test mass in the gravity field. Providing the same accuracy achieved with previous versions, the instrumental improvements mainly concern size, weight, data processing algorithms and operational simplicity. An uncertainty of 9 μGal (1 μGal=1×10–8 m·s−2) can be achieved within a single observation session, lasting about 12 h, while the time series of several observation sessions show a reproducibility of 4 μGal. At this level, gravity measurements provide useful information in Geophysics and Volcanology. A wide set of dynamic phenomena, i.e. seismicity and volcanic activity, can produce temporal gravity changes, often quite small, with an amplitude ranging from a few to hundreds of microgals. Therefore the IMGC absolute gravimeter has been employed since 1986 in surveying the Italian active volcanoes. A brief history of the gravimeter and the description of the new apparatus, together with the main results of ongoing applications in Geophysics and Volcanology are presented

PROCEDURA DI CONFRONTO E ANALISI DEI RISULTATI NEL CONFRONTO FRA CAMPIONI DI FORZA DEI CENTRI ACCREDITATI

Nei mesi di marzo e aprile 2012 è stato eseguito un confronto sperimentale tra le macchine campioni primari di forza dell’INRIM e i campioni di forza dei Centri accreditati per la taratura delle catene dinamometriche, applicando la forza solo in compressione. L’obiettivo del confronto è stato quello di verificare le incertezze dichiarate dai Centri.During March and April 2012 was made an experimental comparison between the primary force standard machines INRIM and machines force of centers accredited for calibration of dynamometer chains, applying force only under compression. The objective of the comparison was to check the uncertainties declared by the Centers

An international comparison of surface texture parameters quantification on polymer artefacts using optical instruments

An international comparison of optical instruments measuring polymer surfaces with arithmetic mean height values in the sub-micrometre range has been carried out. The comparison involved sixteen optical surface texture instruments (focus variation instruments, confocal microscopes and coherent scanning interferometers) from thirteen research laboratories worldwide. Results demonstrated that: (i) Agreement among different instruments could be achieved to a limited extent; (ii) standardised guidelines for uncertainty evaluation of areal surface parameters are needed for users; (iii) it is essential that the performance characteristics (and especially the spatial frequency response) of an instrument is understood prior to a measurement

Caratterizzazione di boccole pneumostatiche ad asse singolo orizzontale

Il lavoro illustrato nel presente Rapporto è stato svolto nell’ambito di un contratto di ricerca tra l’INRIM e la cocietà MAGER s.r.l. per lo studio sulla “caratterizzazione delle specifiche geometriche e cinematiche di boccole pneumostatiche”. Nell’ambito del contratto sono state definite le seguenti attività: a) progettazione e realizzazione del sistema di applicazione del carico e di misura b) misura di: • coppia minima di primo distacco • coppia di attrito cinetico c) valutazione della max coppia torcente limite (oltre il quale le caratteristiche del sistema sono irrimediabilmente alterate) applicabile al sistema, per applicazioni di torsiometria d) misura delle caratteristiche pneumostatiche principali: • portanza radiale limite • rigidezza radiale massima Per le attività indicate è stata messa a disposizione dei tecnic dell’INRIM una boccola pneumostatica ad asse singolo orizzontale tipo TR 160 130 R costruita dalla Società MAGER S.r.l