Development Of Induction Current Acquisition Device Based On ARM

Time domain aeronautical electromagnetic method is by means of flight platform,equipped with electromagnetic exploration equipment,the underground media for rapid measurement of the detection method.During the exploration process,due to the limitation of ATEM system detection mode,the power of transmitting power is too large and the measurement method is not accurate,it is difficult to directly measure the emission current waveform at full power,which affects the detection accuracy.Therefore,the multi-turn closed loop is used as wire-loop,ATEM system is used to fly on the area where the wire-loop fixed,by measuring the induced current in the wireloop to restore the emission current waveform.This method can not only obtain the key parameters such as duty cycle,amplitude and turn-off time of the emission current,but also the performance of the transmission system can be evaluated by the obtained current waveform.Induction current has the characteristics of fast attenuation,small signal amplitude,etc.,and need to use high-resolution,high sampling rate of the instrument to acquire.At present,there is no special collection instrument for the induction current of wire-loop.Most of them are collected by universal modular acquisition device,and the resolution and sampling rate can not meet the acquisition requirements.In view of the above problems,this paper designs and realizes the acquisition device for the wire-loop induction current,the main work is as follows:(1)The principle and calculation formula of the induced current in the wire-loop are introduced.The induction current is simulated by Matlab.According to the simulation results,the index of the induction current acquisition device is put forward,and the overall design of the induction current acquisition device based on ARM is completed.(2)Aiming at the low noise design of the induced current acquisition system,the design of the low noise acquisition device is carried out from three aspects: analog circuit and device selection,independent power supply structure and high frequency electromagnetic interference suppression.The test results show that the effect of noise suppression is obvious.(3)Aiming at the real-time data storage problem of ARM acquisition device,the data storage technology based on DMA + ping-pong buffer and the data storage technology of multi-task priority are put forward.The fast calculation method of data based on Qt and C ++ is studied,and the solution speed is about 2.8 times higher than the Matlab program with the same solution.(4)Based on the hardware platform and the software platform,the design of the cRIO acquisition device is completed.The acquisition of the induced current waveform is realized.Finally,the defects of the cRIO acquisition device are analyzed.(5)The performance test and comparison test of the ARM acquisition device are completed.The induction current test of the wire-loop with different time constant and different height is carried out,which proves the accuracy and stability of the ARM acquisition device.