The Effects Of Seismic Noise And Discharging Wire For The Performance Measurement Of Inertial Sensor Based On Torsion Pendulum Scheme

The high-precision inertial sensor has been widely applied in the fields of space sci-ences and technologies. For the satellite gradiometry mission which can obtain the global gravity data, its key payload is a high-precision gradiometer which is constructed of six high-precision electrostatic accelerometers with a resolution of above 2×10-12 m/s2/Hz1/2 in the frequency range of 5mHz～0.1 Hz. On the other hand, the object in space can fly along geodesic for a long time, so the gravitational experiments using inertial sensors in flight can obtain better result. The noise of the inertial sensor in LISA project which is used to detect gravitational waves should be lower than 3×10-15 m/s2/Hz1/2 at 0.1 Hz.An electrostatic accelerometer with a resolution of the level of 10-10m/s2/Hz1/2 has been developed and tested with the method based on a two-stage pendulum in our group. Its resolution is not enough for the satellite gradiometry, so a series of improvement should be done based on the present progress. At the same time some noise sources should be carefully considered in ground measurement.In this thesis, the working principle of the electrostatic accelerometer and the improved design based on the accelerometer have been firstly introduced, and some elements affecting the performance of the accelerometer are discussed. Then an improved test scheme based on a two-stage pendulum is designed, and the noise level of the test experiment is also estimated.Secondly, performance investigation of an inertial sensor on ground is more or less limit by the seismic noise. For a two-stage pendulum inertial sensor test scheme, ground vibration or seismic noise is not directly coupled to the input port of the sensor, it will be attenuated through a transfer function. The transfer function of any type of fiber suspension test scheme is strictly analyzed and validated by experiment perfectly.The test mass of inertial sensor such as accelerometer is discharged with a thin conductive wire in order to suppress the effect of the residual charge and environmental electromagnetic field. The mechanic linkage of this wire will introduces additional thermal noise. A simple high quality factor torsion pendulum is used to measure the stiffness and loss angle of this thin wire. The stiffness and quality a 10μm gold wire is measured with this facility, then the relationship of the stiffness and loss angle versus the material and shape of thin conductive wire is also investigated tentatively.