Development Of Portable Full-wave MRS Receiving System In Underground Engineering

With the development of infrastructure construction at top speed in our country,underground engineering construction occupies a more and more important part.Magnetic resonance sounding(MRS) technology as a kind of direct detection method,is applied in underground engineering to detect occurrence state of disaster water, thispromoting the prevention and control of water disaster in underground engineering.However, the existing MRS instruments in the underground environment have manydeficiencies, Such as:The instrument has large volume and heavy weight so that innarrow underground environment is not easy to carry; Data collection methods cannotbe satisfied to the underground environment or to record complete MRS signals forthe post-processing; PC system data operation takes long time. This paper analyzedthe above problems, proposed overall design of portable full-wave MRS receivingsystem in underground and developed the prototype success. Through laboratory andfield experiments, the stability and reliability of the system has been validated.This paper aiming underground engineering environment, combined with thebasic principles of underground magnetic resonance signal detecting, designs thereceiving system from the probe field and ways. In portable design, followlightweight structure, easy operate, stable and reliable principles, using portable touchtablet as a PC platform embedded within the system reducing the instrumentconnections. And the internal skeleton using stainless steel to build, adopted modulardesign, making system compact and lightweight. The weight of receiving system is7.5kg. This development provided a portable receiver for MRS detection inunderground engineering.In the signal receiving performance design, as the detection space ofunderground is limited, on the basis of modeling and theoretical calculation to thereceiving antenna, this article adopts the μmeter levelμ of receiver coils separated from transmitter to receive MRS signal. And for matching the series coils, design afront-end matching network and a follow-up amplifier unit so that the output MRSsignal can be amplified80.6~130.1dB; Based on low-noise MPS-140801acquisition card realize full-wave MRS signal acquisition, which the maximumsampling rate is128ksps. Meanwhile, collecting calibration circuit designed togenerate a calibration signal to calibrate phase of superimposed signals more accurate.Superimposed accuracy of signal acquisition is not greater than78μs; System timingbuilt from both hardware and software: The software setting transmit, release,switching and acquisition time, the hardware circuit design for accurate controlinstrumentation systems timing; Develop system PC software based on LabVIEW,designed from three levels respectively are the user input layer, the hardware driverlayer and system processes layer. The mode of software is mainline single-threadedand branch-line multi-threaded. Build the "producer-consumer" multi-threadedarchitecture for data processing cycle. Data transfer rate compared with the originalsystem is more than4times. This method ensures the large data received from thesystem efficiently in the underground environment.Eventually, the article tests the overall performance on the underground portablefull-wave receiving system. The tests include noise shielding laboratoryenvironmental testing, the instrument background noise testing, simulation MRSsignal testing and the equipment in the field environmental testing. The systembackground noise is10.51nV and the short-circuit equivalent noise is1.76nV/Hz.The test results were analyzed to verify the stability and reliability of thevarious parts of the receiving system.