| The method often used in seafloor sulfide exploration is the ocean self-potential method,which can roughly determine the location of the sulfide ore body by measuring the seabed selfpotential anomaly.In recent years,most parties have used the ship-borne deep towing method.The receiver and electrodes are dragged by the ship-borne deep towing cable to perform underwater single-direction electric field measurement.This operation method is time-consuming and laborious,and the tow body cannot be close to the seabed.The measured signal The signalto-noise ratio is low,and the measurement line is relatively single.The self-potential SP measurement system onboard has the problems of large volume,large weight,and high power consumption.The research on the SP measurement tool described in this article is based on the Second Institute of Oceanography of the Ministry of Natural Resources.It has developed and designed a set of small size,low power consumption,high integration,which can be used for SP measurement on autonomous underwater vehicles AUV.The tool can collect,store and transmit the weak electric field triaxial signal in the marine environment.SP measurement tools include acquisition cabin,ocean electrode,cable and supporting upper computer system.The working process is divided into four steps: parameter setting,towing body installation,underwater measurement,and data transmission.The collection cabin is connected to the host computer through a cable USB interface to complete the status check,clock calibration,and collection settings.After the configuration is completed,the collection cabin and ocean electrodes are installed on the AUV body or towed platform to carry out underwater electric field potential measurement.After collecting and recovering the body,connect the upper computer via USB to export the data file for subsequent data processing and analysis.The system master MCU chooses to use the STM32F4 series microcontroller,which is based on ARM's 32-bit Cortex-M4 core processor,which has the advantages of high performance and low power consumption.Other peripheral circuits designed include power conversion module,ADC acquisition module,real-time clock RTC,NANDFLASH storage module,USB data transmission module,charging module,etc.The overall circuit is equipped with a lithium battery loaded in a 50mm×350mm cylindrical collection cabin.The air weight is 1.3kg and the underwater weight is 0.6kg.It has the characteristics of strong reliability,small size,and low power consumption.It can work continuously for more than 72 hours in a water depth of 4000 m,with a range of ±39m V and a sampling rate of 50 Hz.,It has 4GB large-capacity storage space,and is designed with corresponding upper computer software to realize the functions of control acquisition and shutdown,time calibration,lower computer status query,file download,USB charging and so on.The overall system has passed the indoor test experiment.The noise floor level of the circuit is better than 10 n V/rt(Hz)@1Hz,the dynamic range reaches 119 d B,the power consumption in sleep mode is about 2.5m W,and the power consumption in acquisition mode is about 325 m W,which meets the design requirements..Participated in the Southwest Indian Ocean hydrothermal sulfide survey voyage organized by the Second Institute of Oceanography of the Ministry of Natural Resources from February to April 2021.The SP measurement tool collected 6spontaneous potential survey lines and operated for 25 hours,achieving good and effective levels Electric field and vertical electric field data,and observations of natural potential abnormalities caused by suspected sulfide deposits.The sea trial results show that the equipment can work stably and effectively. |
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