Preliminary Research Of The Delta-sigma Modulation Technique In Digital Output Sensor

Seismology is essentially an observational science.Seismic observation provides continuous,reliable and complete basic data for people to record,analyze and study the internal structure of the earth,determine the kinematics and dynamics parameters under different seismic source models,and so on.Seismic observation requires the support of observation stations and various seismic instruments.At present,my country has established a complete digital seismic observation system,but it is greatly affected by the surface.The use of underground observation methods is an effective way to avoid all kinds of surface interference and improve seismic monitoring capabilities.It is also important to measure stress and strain directly in the deep underground.Means,an effective way to improve the quality of observational seismic data.The downhole comprehensive observation system combines multiple sensors together,and the monitoring signals are numerous and complex.If the sensor is only placed downhole,a large number of analog signals need to be transmitted from downhole to the surface.The difficulty of implementation increases rapidly with the increase of the number of signal lines,and technical problems such as signal crosstalk need to be overcome.In order to solve this problem,a distributed data collector is often used,that is,the analog-digital conversion function is closely combined with the observation sensor,the analog-digital conversion circuit is adapted to the characteristics of the sensor output signal,and the sensor and the data collector are fixed and integrated to improve Observe the overall performance of the system.This article has studied the delta sum modulation technology in depth,which is a feedback loop composed of an integrator,an analog-to-digital conversion chip and a digital-to-analog conversion chip,and a low-pass digital decimation filter is configured outside the feedback loop.It integrates three core technologies: oversampling,quantization noise shaping,and digital low-pass decimation filter.This paper proposes a design method of placing the amplifier and phase-sensitive detector in the digital output sensor in the incremental sum feedback loop to form a large feedback loop.This method not only retains the three characteristics of the incremental sum modulation technology,but also It is beneficial to suppress the measurement errors generated by the phase-sensitive detection and preamplifier,and improve the accuracy and stability of the entire digital measurement system.Aiming at the design method,the thesis has carried out work from three aspects:model derivation,simulation and experiment test.Based on the incremental sum modulation technology,the thesis applies the demodulation circuit of the microdisplacement measurement sensor to the inner incremental sum modulation loop to suppress the error of the amplification and demodulation circuit and improve the overall performance of the loop;The circuit model in which the amplifier and phase-sensitive detector are placed in the incremental sum modulation feedback loop has been theoretically analyzed and simulated.The feedback loop's suppression of errors and the influence on the measurement range and other parameters are studied;according to the circuit model,The circuit board was designed and manufactured,and the control software and digital filtering and extraction software were written,and tests and experiments were carried out on the experimental circuit,which achieved the expected research goals.