The influence of the selection of zero-crossing starting point on measurement accuracy of the absolute gravimeter

Abstract

The absolute gravimeter is an important precision instrument for obtaining gravity acceleration in fields such as geophysics, resource survey, and national defense construction. It is greatly affected by its self-vibration during operation. If the self-vibration frequency exceeds the range of the sensor, it will not be effectively processed by the method of vibration compensation. To solve this problem, the effect of instrument self-vibration on the accuracy of gravity is analyzed through simulation and actual measurement data. Based on the calculation of the simulation data, the functional relationship between the self-vibration frequency of the instrument and the zero-crossing starting point is obtained. The Starting Point Mathematical Model is established to accurately calculate the zero-crossing starting point. Then, the zero-crossing starting point calculated by the model is taken as the time reference of the zero crossing for the least square fitting. The split and platform absolute gravity measurement systems are built, respectively, to test the measured data. The test results reveal that, compared with the traditional method using the initial falling time as the zero-crossing starting point, the proposed method can reduce the gravity deviation by 50 μGal and improve the accuracy by an average of 35.35% under split-type working conditions. Under platform-type working conditions, it can decrease the gravity deviation by 3 mGal and improve the accuracy by an average of 53.78%. The method proposed can reduce the fixed phase vibration interference caused by the instrument self-vibration and provide a reference for improving the measurement accuracy of the instrument under different working conditions.