Possible large systematic error source in absolute gravimetry

摘要

We have investigated large systematic errors, exceeding several parts in 10~(8) (several tens of microgals), in absolute gravity measurements with the aim of reducing the differences in measured gravity values obtained by different kinds of absolute gravimeter. We find that rotation of a falling object around a horizontal axis may be induced by small differences in the moment of release of the object from its points of support. This may lead to a large systematic error which seems to be common to all types of absolute gravimeter. We propose a simple model for the rotation of the falling object which may be applied to all kinds of absolute gravimeter and predict errors of as large as 10~(-6) ms~(-2) (100 μGal) which are confirmed by experiment. To reduce the error it is necessary to minimize both the area of the contacting surface and the stress applied to it. It is also necessary to monitor the rotation of the falling object in order to show that there is no systematic error in measured gravity values.