Research On Related Technical Issues For Dynamic Calibration Of Seismometers

Based on China Earthquake Administration Program "Auxiliary experiment platform for very-low frequency vibration test of seismometers",research on related technical issues for dynamic calibration of seismometers was done in this dissertation.In chapter 1,the background,the purpose and the content of the dissertation were presented.First,main calibration parameters and common calibration methods were introduced.Secondly,the present research status of calibration methods of seismometers at home and abroad was analyzed.Thirdly,the development trend of seismometers calibration was pointed out.At last,the main research content and aim of the dissertation were addressed.In chapter 2,overall design of dynamic calibration system for seismometers was introduced.First,overall structure and working principle of dynamic calibration system were studied.Secondly,hardware components of calibration system and dynamic calibration software for seismometers were introduced.In chapter 3,dynamic calibration technology of seismometer frequency characteristic was researched.First,theoretical frequency characteristic model of seismometers was established based on seismometers structure.Secondly,calibration methods for magnitude-frequency characteristic and phase-frequency characteristic were researched.Thirdly,influences on calibration of frequency characteristic that result from signal distortion were researched and simulated,then the processing method for dynamic calibration under signal distortion was proposed.At last,dynamic calibration procedure of seismometers was designed.In chapter 4,design technology of fixture for seismometers was researched.First,influences on calibration result arose from transverse vibration and orthogonality inclination angle were analyzed scrupulously.In the meantime,measure method of orthogonality inclination angle was put forward.Secondly,structure design was finished under consideration of the demands on structure and mass and influence on the measurement results.At last,dynamic analysis was carried out based on ANSYS.In chapter 5,magnetic shielding technology in the process of low frequency calibration was studied.First,influence of magnetic field on calibration was evaluated.Secondly,magnetic leakage of permanent magnet and electrified coil were analyzed.Thirdly,the correlative equation between magnetic shield effectiveness and the parameters of the structure and the material was established to provide guidance for the design of a magnetic shield case.Finally,a magnetic shield case was designed for low frequency calibration.In chapter 6,the dynamic calibration system for seismometers was researched experimentally.First,dynamic performance of fixture was tested.Secondly,the influence on calibration results caused by signal distortion was researched experimentally,which proved the feasibility of processing method for dynamic calibration under signal distortion.Thirdly,influence on calibration results arose from orthogonality inclination angle was researched experimentally,which proved the correctness of the method to test orthogonality inclination angle.Then,experiment for magnetic shielding technology was carried out to verify the effectiveness of the magnetic shielding case.Finally,frequency characteristic and amplitude linearity of seismometers was researched,which proved the effectiveness and reliability of the applied methods.In chapter 7,the achievements of this dissertation and future research were summarized.