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Free-fall gravitational acceleration measurement using a pneumatically controlled catch-and-release-system in a semi-rotating vacuum chamber

Mokobodi T., Greeff P., Kruger O., Theron N. J.

Metrology and Measurement Systems

2018

Vol. 25, nr 4

689--699

Knowledge of gravitational acceleration in metrology is required for traceable force and pressure calibrations, furthermore the redefinition of the SI base unit of kilogram requires absolute accomplishment of the gravitational acceleration. A direct free-fall gravimeter is developed using pneumatic grippers for test mass handling and a semi-rotary actuator for repositioning, i.e. automated re-launching. The catch and release system is powered by compressed air. This eliminates electric interferences around the test mass. A simplified method of signal capturing and processing is used on the designed gravimeter. A digital frequency trigger is implemented in the post processing algorithms to ensure that the signals are analysed from the identical effective height. The experimental results measured the site gravitational acceleration of 9.786043 ms -2 with a statistical uncertainty of ± 29 μs-2.