Test and Measurements conference 2016 DESIGN AND DEVELOPMENT OF FREE FALL ABSOLUTE GRAVITY MEASURING SYSTEM USING PNEUMATIC ACTUATORS

Gravitational force and acceleration measurement devises have been in continuous development with the objective to improve the method for realizations of the gravitational acceleration measurand accurately. The accuracy requirements from the field of metrology, geodesy, geophysics and mineral exploration led to these developments. In metrology, knowledge of gravitational acceleration is required in force and pressure calibrations which are linked to SI base units. Redefinition of SI base unit of kilogram also requires accurate measurements of gravitational acceleration, which is tied to the standard SI units of length and time. Length and time measurement must be achieved with error of 10 -9 or less to comply with the requirements in metrology. Experiments are performed using free fall gravimeter using 633 nm wavelength He-Ne laser with the Michelson (improved) interferometer setup to achieve these requirements. This paper discusses the method of direct free fall gravimeter designed and developed at the National Metrology Institute of South Africa using a simplified launching and capturing mechanism in the rotating vacuum chamber. Numerical simulations and signal processing method along with their results are discussed. The results of initial prototype are presented and discussed along with projected system improvements in working toward fully functional system, the average error of the prototype is found to be 5 parts in 10 4 .