Precise definition of the effective measurement height of free-fall absolute gravimeters

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  • Ludger Timmen

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OriginalspracheEnglisch
Seiten (von - bis)62-65
Seitenumfang4
FachzeitschriftMETROLOGIA
Jahrgang40
Ausgabenummer2
PublikationsstatusVeröffentlicht - 1 Apr. 2003

Abstract

For up-to-date absolute gravimeters, the trajectory of the test mass during a free-fall experiment (drop) is about 20 cm along the vertical, and the corresponding gravity change is about 60 × 10-8 m s-2. The reference height of the derived free-fall acceleration g has to be defined with an accuracy of 1 mm to 2 mm within the dropping distance to preserve the accuracy of the measurement system (e.g. FG5: 1 × 10-8 m s-2 to 2 × 10-8 m s-2). The equation of motion comprises a vertical gravity gradient to take the height dependence of g into account. In general, a linear vertical gravity gradient γ is introduced that has been measured by relative gravimeters. In that case, the g-value refers to the origin of the coordinate system (z = 0), which is normally the starting position of the drop. In the case of an unknown or uncertain gradient we recommend an alternative approach. A simple parabolic equation (assumption γ = 0) can be used to evaluate the time/distance data pairs, and later these g-determinations have to be corrected for the vertical gravity gradient using the effective measurement height. The solution presented is not restricted to low initial velocities. It considers time/distance measurements equally spaced in distance. Also, in extreme cases, unknown non-linearities within the vertical gravity gradient do not significantly affect the result of the absolute gravity determination.

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Precise definition of the effective measurement height of free-fall absolute gravimeters. / Timmen, Ludger.
in: METROLOGIA, Jahrgang 40, Nr. 2, 01.04.2003, S. 62-65.

Publikation: Beitrag in FachzeitschriftArtikelForschungPeer-Review

Timmen L. Precise definition of the effective measurement height of free-fall absolute gravimeters. METROLOGIA. 2003 Apr 1;40(2):62-65. doi: 10.1088/0026-1394/40/2/310
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