| Earthquakes are vibrations caused by the rapid release of energy from the crust,and are Seismic wave generated during the vibration of the crust.Picking up seismic observation instruments to provide scientists with scientific observation data often requires observation instruments to achieve high technical indicators and good stability.Differential capacitance sensors are widely used in seismic observation instruments,such as telescopes,gravimeters,and borehole strain gauges.The differential capacitive sensor amplifies,filters,and detects the collected signal before sending it to the data collector.The data collector converts the analog signal output by the sensor into a digital signal output after analog/digital conversion.If the instrument is working in the open loop state,the noise generated by the amplifier,the switching noise generated by the phase sensitive detection and the Quantization error generated by the ADC in the quantization process will directly appear in the output signal,which will adversely affect the measurement accuracy of the signal detection circuit.In order to improve the accuracy of the signal detection circuit of differential capacitive sensors,this paper proposes a method that combines incremental sum modulation technology with differential capacitive sensors to create a new type of signal detection system.The signal detection circuit expands the feedback loop of the incremental sum modulator to the front end of the amplifier,and places the preamplifier and phase sensitive detection circuit in the feedback loop of the incremental sum modulator to form a large feedback system.According to the theoretical derivation results,the method designed in this paper not only retains the three characteristics of the Delta Sum Modulation technology,namely Oversampling,Quantization error shaping and low-pass digital decimation filtering,but also effectively suppresses the noise brought by the preamplifier and phase sensitive detector,and improves the measurement accuracy and circuit stability of the signal detection system.In this paper,theoretical derivation,circuit design,programming and differential capacitance sensor device fabrication are studied.On the basis of incremental sum modulation technology,the preamplifier and phase sensitive detector are placed in the feedback loop of incremental sum modulation to improve the accuracy and stability of circuit measurement.In order to verify the design scheme,this paper also made a differential capacitive sensor device,and combined this device with the signal detection circuit experimental board,carried out experiments and Test effort.The experiment shows that the output digital quantity of the signal detection circuit has a high correlation with the magnitude and direction of the deviation from the balance position of the central plate,indicating that the working state of the circuit board is normal,and indicating that our proposed signal detection scheme using incremental sum modulation technology is feasible. |
