Research On Key Technology Of High Precision Seismic Precursory Data Acquisition Based On Multi-skew Integration

With the development of geophysical observation theory and technology,the demand for high-performance seismic precursory observation instruments is increasing.Data acquisition system is the key equipment of precursory observation,and its performance directly affects the data quality of precursory observation.At present,most of the A/D conversion modules used in precursory data collector are sigma delta A/D converter,so the performance of data collector is limited by the performance of A/D conversion chip.The supply of high-performance A/D converter chips is easy to be limited.More than 24 bit A/D converters are very scarce in the market,and the cost is high,which seriously limits the large-scale use and promotion of seismic observation instruments.Therefore,it is of great significance to find another way to study the high-performance data acquisition technology suitable for earthquake precursor observation.In this paper,a data acquisition scheme based on multi slope integral A/D conversion technology is proposed.According to the characteristics of low sampling rate and high resolution of precursory observation,the integral A/D conversion technology is introduced into the data acquisition system,which provides a relatively new technology exploration way for the research of seismic observation data collector.A high stability voltage reference and a high resolution time interval measurement circuit are designed to improve the stability of integration and the resolution of conversion.In this paper,the multi slope integral A/D conversion technology and its application in seismic precursor data acquisition system are studiedA data acquisition scheme based on multi slope integral A/D conversion technology is proposed.On the basis of double oblique integration A/D conversion technology,the multi oblique integration technology is studied to improve the conversion resolution.The hardware and software scheme of A/D conversion of multi slope integral is given.Research on high stability voltage reference.The ltz1000 voltage reference chip is used as the core to design a voltage reference to obtain a high stability voltage reference and provide a reliable reference voltage for the integral circuit.The experimental results show that the time stability of the reference source is 1.9ppm/h.At the same time,the module can be widely used in other precision measurement fields.Research on precise time interval measurement technology.In order to improve the measurement resolution of integral time interval,the time to digital conversion technology is studied,the related hardware and software design is completed,and the test and analysis are carried out.The experimental results show that the standard deviation is less than 450 ps for the time interval less than 1ms and less than 53 ps for the time interval less than 100 ms.Research on seismic data denoising algorithm.Combining wavelet algorithm with empirical mode decomposition algorithm,an improved seismic data denoising algorithm is proposed to reduce data noise and improve measurement quality.And the software implementation results of the algorithm are given.The experimental results show that the improved algorithm is better than the single wavelet denoising algorithm and empirical mode decomposition denoising algorithm for non-stationary signals.The theoretical methods and key technologies involved in the above research are studied and discussed,and the specific schemes of hardware and software are put forward.Simulation experiment,test and numerical experiment are designed to verify the effect of the scheme.The functions and parameters of each module are tested,and the related algorithms are tested by numerical experiments.The results show that the voltage reference stability and time interval measurement resolution meet the expectations,the design scheme meets the measurement requirements,and the noise reduction effect of the improved algorithm is better than the single wavelet algorithm and empirical mode decomposition algorithm,which has certain theoretical significance and engineering application value.