Research On Fiber Optic Pulse High Current Sensing Technology

Accurate measurement of pulse high current plays important roles in many fields,such as electromagnetic emission,electromagnetic ejection,high-power laser,electromagnetic pulse,nuclear physics,biomedicine,environmental engineering and so on.Compared with shunts and Rogowski coils,fiber current sensor has high measurement accuracy,wide frequency response range,large dynamic range,good insulation,strong resistance to stray magnetic field interference,and good traceability which is based on the Faraday magneto-optical.Therefore,fiber current sensor is the best solution for the measurement of high current.Aiming at the demand of accurate measurement of pulsed large current,the main research work and conclusions of this paper are as follows:1)Design of measurement system for fiber pulsed high current sensor.An interferometric digital closed-loop measurement scheme is proposed,which uses the 2? square wave modulation method to improve the detection sensitivity of the sensor.Besides,the digital phase-locked amplification technology is used to implement the Faraday phase-shift demodulation method to effectively extract weak current signals under strong noise;A cyclic storage-triggering scheme is designed based on FPGA RAM IP core to achieve complete capture of high current pulses;Based on Lab VIEW,visual measurement software of pulse high current is designed.2)Research on broadband characteristics of fiber pulsed high current sensor.A sensor dynamic model of high-order discrete domain is build based on Simulink and a digital measurement method of forward gain is proposed based on open loop,which effectively help avoid resistance error of the resistor;A result is proposed that in closed-loop signal detection system,the forward gain and output moving average filter order are the main factors affecting the measurement bandwidth of the sensor.By simulation,the forward gain and filter order are optimized,which not only suppresses the overshoot,but also improve the measurement accuracy and bandwidth of the sensor.3)Research on nonlinear generation mechanism of sensor measurement error.The optical path model of the fiber pulse high current sensor is deduced through the Jones matrix,and a conclusion is made that the error of the azimuth and phase delay angle of the fiber quarter-wave plate is one of the main reasons for the nonlinearity of the measurement error of the fiber pulse high current sensor;A piecewise linear interpolation compensation method is proposed to improve the non-linear error of the sensor.After compensation,the measurement error of the sensor is reduced from a maximum of 0.6% to less than 0.1%.4)Calibration device construction and field application.A fiber optic pulse high current sensor calibration device is build,wit h the calibration,the measurement error of the designed sensor is reduced to less than 0.1% and the measurement bandwidth is much higher than 10 k Hz in the current range of 0 ~ 300 k A;The design principle prototype is applied to short-circuit high-current experiments,welding machine high-current experiments and other field tests,the results show that the sensor has high current pulse measurement performance.