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

Multiwavelength Interferometry for Geodetic Lengths

Working Group 5.42

Profile

WG 5.42 is concerned with the traceable realization of distances from around 30 cm to one kilometer. It conducts research and development in the field of absolute interferometry with refractive index compensation, maintains the national standard (the so-called geodetic basis) in this field, provides calibrations of laser-interferometer systems, of electronic distance-measuring devices and of precision tape measures, and participates in corresponding standardization committees at DIN, ISO and SCGD.

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Research/Development

 

 

 

 

The primary focus of our work in research and development is on the development of new interferential measurement methods (and on the further development of existing methods) for the traceable measurement of large distances with low uncertainties, especially under realistic external conditions. Our goal is to implement these measurement methods in our Working Group’s range of services, and to apply these methods to precision engineering and geodesy.

Projects

Current projects

 

 

 

Opens internal link in current windowCompleted projects since 2005

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Services

 

 

 

WG 5.42’s field of work is the calibration of one-dimensional length-measuring instruments whose measuring ranges extend from a few centimeters to several hundred meters. To this end, we have two highly specialized standards at our disposal: the geodetic basis and the 600 m baseline. Below, you will find standard services in the field of length-measuring instruments and laser interferometers for which a calibration certificate can be issued with a CMC seal; these services are accredited in accordance with CIPM-MRA. For special challenges, however, customized solutions can also be jointly worked out in discussions. If required, we can also provide special calibrations for measuring probes (e.g. calibrations for specific geometries).

 

 

Calibration of Laser InterferometersCalibration of Laser Interferometers

Measurand

Range

Expanded Uncertainty

Laser-interferometer system: error of indicated displacement with refractive index compensation L

to 2 m
α = 0 K-1
15°C to 25°C

Q[0,015; 0,031 L] in µm, L in m

Laser-interferometer system: error of indicated displacement with refractive index and thermal expansion compensation L

to 2 m
α : arbitrary
15°C to 25°C

Q[0,015; 0,074 L] in µm, L in m
(e.g. for the coefficient of thermal expansion
α = 11,5.10-6.K-1)

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Calibration of length measuring systemsCalibration of length measuring systems

 

Measurand

Range

Expanded Uncertainty

line scale, steel

to 4 m

Q[5,8; 1,8 L] in µm, L in m

line scale, invar or glas

to 4 m

Q[5,8; 0,4 L] in µm, L in m

tape, overlay, steel

to 50 m

Q[13,4; 2,6 L] in µm, L in m

tape, overlay, steel

50 to 100 m

Q[132; 2,6 (L-50 m)] in µm, L in m

tape, overlay, invar

to 50 m

Q[13,4; 0,72 L] in µm, L in m

tape, overlay, invar

50 to 100 m

Q[41; 0,72 (L-50 m)] in µm, L in m

tape, sagging, steel or invar

to 50 m

Q[40; 3 L] in µm, L in m

Laser range finder (EDM), flat reflector

to 50 m

460 µm

aser range finder (EDM), retroreflector

to 50 m

102 µm

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Calibrations for probe

On request are calibrations available in special geometry for probe developed and offered.

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Information

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