Research On Some Issues About Data Acquisition Unit In Geophysical Exploration Equipment

Geophysical exploration,also known as applied geophysics,is an exploration method established based on the study of differences in physical properties of rocks and ores.It uses instruments to observe the distribution of various geophysical fields,analyzes the observation results,solves geological problems,and is widely used in environmental engineering surveys and geological prospecting.It is of great significance to the development of social economy.With the continuous progress of science and technology,people have established a series of geophysical exploration methods,such as transient electromagnetic method,gravity exploration method,seismic exploration method,etc.Due to the high precision and resolution of seismic exploration methods and large exploration depth,they are widely used in the field of oil and gas exploration.This laboratory has designed a multi-level,distributed seismic data acquisition system.The system is mainly composed of Host Control Unit,Line Management Unit,Battery Management Station and Data Acquisition Unit(DAU).The DAU is directly connected to the sensor module to read data.All the DAU are managed in regions.The DAU in each region is managed by a power station.The power station in each region is managed by a cross station.The host only needs to manage the number Fewer intersections are enough.This way increases the scalability and reliability of the system.Based on the original design,this paper studies three problems in the DAU.The first is the power supply problem of the sensor module.The Data Acquisition Unit uses a switching power supply to convert high voltage to low voltage to power the sensor module.The sensor module uses a high-precision analog to digital converter(ADC).How much noise does the switching power supply have on the ADC performance?What is the path of influence?In this paper,a theoretical analysis of this problem is carried out,and a test circuit is designed.A power analyzer is used to add a sine wave of known frequency and amplitude to the ADC power supply as power supply noise.Observe the performance of the noise on the ADC output spectrum.There are two forms of power supply noise,one is direct coupling noise,which is generated by the attenuation of the input power supply noise through the power supply rejection ratio;the other is intermodulation noise,which is generated by the direct coupling noise and the intermodulation of the input signal,of which the second order Intermodulation noise is the main component,and when the input signal is large,the second-order intermodulation noise will be greater than the direct coupling noise.The test results also show that the ripple and noise of the switching power supply have a limited impact on the ADC with a high power supply rejection ratio.Therefore,in the scenario of pursuing the power supply efficiency,the switching power supply can be used directly to power the ADC.The second is the issue of multi-rate and rate negotiation.Existing DAU support a data transmission rate of 4.096Mbps.In order to achieve more connection of DAU,the support of the DAUs for 8.192Mbps and 16.384Mbps data transmission rate is added.In practical applications,it is sometimes necessary to add a new DAU to a system that has already been deployed.If the new DAU cannot know the data transmission rate of the DAU in the system,a connection cannot be established.Therefore,a rate negotiation function needs to be added to the DAU.The DAU uses 4.096Mbps as the negotiation rate to establish a connection with other DAUs.After the connection is established,the transmission rate is negotiated by sending data packets to each other.Through rate negotiation,the newly added DAU can obtain the data transmission rate of the system,and The adjustment of its own data transmission rate is consistent with the system.The third is the problem of automatic routing.In order to upload the data back to the data center in real time and ensure the integrity of the data,an automatic routing function is added to the DAU so that when a data link fails and the data cannot be uploaded,the DAU can Automatically find a new data transmission path and upload data through the new path.