Abstract: To solve the problem of real-time monitoring and harmonic analysis of current signals in circuits，a high precision mutual inductance current signal detection device based on FFT ( Fast Fourier Transform) is designed by using sensor technology． The device achieves the purpose of non-contact measurement of loop current signal． It consists of hardware and software． The hardware circuit includes mutual inductance current sensor and detection circuit． The STM32 is used as the main controller performing，Fourier transform to get the frequency and amplitude information of the signal． This microprocessor-based measuring device realizes measurement automation and function diversification，and has certain application value in the industrial field．After detection，the frequency resolution and the amplitude resolution achieve 0． 5 mA，the frequency error of the
current signal is less than 2%，and the amplitude error is less than 5%．

Key words: sensor technology, mutual current signal detection device, non-contact, Fourier transform