Analysis and Optimization of the Recoil-Compensated Absolute Gravimeter

The free-fall absolute gravimeter is commonly used for precise gravitational acceleration measurement. The g value is obtained through quadratic fitting of the position-time data pairs of the freely falling test mass. However, recoil vibrations are generated during the release of the test mass resulting from the movement of the center of mass of the chamber, and errors may arise from these vibrations in the measurement process. To solve the recoil vibration problem, previous researchers have developed the recoil compensation structure to achieve a basically stationary center of mass during the drop. In this paper, counterweights of a variety of masses are tested on our recoil compensated gravimeter, while recoil vibrations are recorded and analyzed accordingly. The multibody simulation indicates that compensated counterweights can significantly reduce the recoil vibration amplitude, making a more precise measurement attainable. In the experiments, accelerometers and seismometers are employed respectively in the simultaneous measurement of recoil vibrations of dropping chamber and reflector. Then all the vibration signals are analyzed and compared, and the outcome confirms the effectiveness of the gravimeter in performing high precision measurement as what is observed in the previous simulations. With a proper design of the counterweight mass, the recoil effect can be significantly reduced during the test procedure, which indicates a potential for high precision measurement.