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Production sequence of Si-spheres and interferometrical determination of the sphere volume

Precision Engineering

Division 5

News from the Annual Report 2009

Fundamentals of Metrology

To achieve the measurement accuracy required for the Avogadro project, apart from new silicon spheres, also improved objectives are required. An optimized spherical interferometer was developed and set up for these high-precision measurements.

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PTB’s sphere interferometer has been used in order to extract precisely the coefficient of thermal expansion (CTE) of 28Si. This is necessary for the spheres of highly enriched 28Si made for the Avogadro Project. For this purpose the diameter of one of the spheres was measured as a function of temperature between 17 °C and 30 °C. It could be demonstrated that the measured deviation of the CTE of 2...

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Bei der Selbstkalibrierung von Winkel-Teilkreisen lässt sich im Falle speziell gewählter Anordnungen von Abtastköpfen zur Auslesung des Teilkreis-Phasengitters ein analytisch vorteilhafter Primfaktor-Algorithmus zur Anwendung bringen. Er ist auch für die Kreuzkalibrierung zweier Teilkreise an-wendbar und erlaubt hierbei eine erhebliche Verringerung des Kalibrieraufwandes.

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Metrology for Economy

A new method for the experimental determination of the effective contact radius of rough microspheres was developed. The results gained by experiment on ruby spheres having a mean diameter of 200 µm are, for normal forces exceeding approximately 300 mN, in good agreement with the theoretical results of the Hertzian equations and with statistically based models for rough surfaces.

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A frequency comb in the microwave range, which is generated by detection of femtosecond laser pulses with a high-speed photodiode, provides a new method for high accuracy length measurements for long distances. A system based on this principle was successfully tested for length measurements up to 100 m.

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Within a study conducted at PTB industrial demands concerning micro-gear metrology and metrologi-cal possibilities in this field were identified. Additionally, the study gives recommendations for further research activities. The traceability of micro-gear measurements is to be realized within a follow-up project.

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Ein neues IT-Konzept für die Referenzsoftware zur Berechnung von Rauheitskenngrößen wurde auf der Basis der anwendungsorientierten Middleware CORBA realisiert, die es ermöglicht, eine Erweiterung der Software auch um externe Module einfach durchzuführen. Damit ist ein tragfähiges, flexibles und zukunftsfähiges Programmgerüst geschaffen worden.

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Metrology for Society

Design and manufacturing of a luminaire positioning fixture

To accelerate and facilitate the workflow in intrinsic safety tests, a new facility was designed and manufactured in cooperation with Department "Intrinsic Safety and Safety of Systems" for the positioning of, e.g., linear (fluorescent) luminaires and various industrial luminaires.[more]

Design and manufacturing of a reference measuring cell for the electric conductivity of ultra-pure water

For the measurement of the electric conductivity of pure water, a new measuring assembly is being set up at PTB. The reference cell is integrated in a set-up used to calibrate measuring cells from industry.[more]

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