21 9 2017 9 Electri c Machines and Control Vol. 21 No. 9 Sep. 2017 1 1 1 1 2 1. 300130 2. 300387 : ( electromagnetic acoustic transducer,emat), EMAT EMAT, EMAT, :, : DOI: 10. 15938 /j. emc. 2017. 09. 014 TG 115. 28 A 1007-449X 2017 09-0103- 07 Design of characteristic signals detecting system for electromagnetic ultrasonic LIU Su-zhen 1 LI Li-bin 1 ZHANG Chuang 1 ZHANG Yan-wei 1 YANG Qing-xin 2 1. Province-Ministry Joint Key Laboratory of Electromagnetic Field and Electrical Apparatus Reliability Hebei University of Technology Tianjin 300130 China 2. Key Laboratory of Advanced Electrical Engineering and Energy Technology Tianjin Polytechnic University Tianjin 300387 China Abstract To solve the problem of low transduction efficiency weak signal and low signal-to-noise ratio SNR in electromagnetic acoustic transducer EMAT system the detection system was designed including EMAT low noise preamplifier broadband receiver and the orthogonal phase-locked amplifier based on the LabVIEW. The difference between the traditional EMAT structure and the new EMAT structure flux density was compared by increasing the intensity of the bias magnetic field can improve the efficiency of EMAT The frequency response characteristic of preamplifier broadband receiver and EMAT were analyzed. The impact of the order filter type and cut-off frequency of the low pass filter to detect the ultrasonic echo signal was studied. Results indicate that the system can achieve the goal of real-time acquisition storage and analysis of electromagnetic ultrasonic echo signal and improve the SNR and resolution of signals. Keywords EMAT SNR preamplifier broadband receiver orthogonal broadband receive 2016-03 - 03 : ( 51307043) ( E2016202260) ( 16JCYBJC19000) : ( 1969 ),,,, ( 1991 ),,, ( 1982 ),,,, ( 1988 ),,, ( 1961 ),,,, :
104 21 0 USB PC LabVIEW SignalExpress Labview Vi 1-3 4 1 Fig. 1 EMAT system based on orthogonal lock-in 5 amplifier 6-7 1. 2 1. 2. 1 8-10 11-14 PCB 15 2 a 2 b Lab- VIEW SignalExpress 1 1. 1 1 Tone-Burst Tone-Burst EMAT 2 Fig. 2 EMAT A /D Structure chart of EMAT
9 105 1. 2. 2 2 d 16 4 COMSOL Multiphysics 40 mm 20 mm 10 mm 60 mm 50 mm 5 mm 0. 6 mm 3 17 3 a EMAT 3 b EMAT 3 a 4 Fig. 4 Preamplifier block diagram Fig. 3 槡 3 3 AD8130 Magnetic field distribution of aluminium plate CMRR 2 MHz CMRR 80 db 10 MHz 70 db AD8130 3 b 10 mm B > 0. 65 T M V N I N 18 V ' N = V N 槡 M 1 I ' N = 槡 M I N 2 5 1 1 / 槡 3 2 3 6 5 mv
106 21 f BW1 = f H1 - f L1 = 1. 429 6 MHz 3 f L1 400 Hz f H1 1. 43 MHz 40 db 4 MHz 38 db 240 Hz 3 MHz 5 Fig. 5 Preamplifier circuit Fig. 6 6 8 Amplitude-frequency curve of preamplifier 5 mv f 1. 2. 3 BW2 = f H2 - f L2 = 15. 464 MHz 4 f L2 36 khz f H2 15. 5 MHz 2 LC 5 LC π 50 Ω 8 7 Fig. 8 Amplitude-frequency curve of preamplifier of Broadband receiver Fig. 7 7 Broadband receiver
9 107 100 khz 10 MHz b 46 μs c 74 μs d 92 μs 2 Q 9 Fig. 9 Connection diagram of EMAT system LO-RF 5 MHz 5 MHz 5 LC 10 Fig. 10 Original signal of electromagnetic acoustic A = 槡 V 2 I + V 2 Q 5 φ = arctan V I 6 V Q 1. 4 MHz V I V Q 2. 6 MHz 0. 1 MHz 11 3 500 mm 200 mm 5 mm 15 mm 1 mm 5 mm 9 4 v 2 910 m /s λ = 0. 727 5 mm λ 2 MHz3 Tone-Burst 11 10 a 2 MHz Fig. 11 Amplitude-frequency curve of EMAT
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