Development Of Small Size Storage Magnetic Field Probe

Based on the shielding effectiveness of small-sized shielded cavities,this study is applicable to magnetic field probes for shielded cavity shielding effectiveness test with no test through-holes and dimensions not larger than 100mm×100mm×100mm or ?150mm×1000mm.The measurement bandwidth is 10kHz~300MHz.The magnetic field probe developed in this paper integrates magnetic field measurement and data storage.After the magnetic field strength is measured,the data is stored in the internal memory chip.After the test is completed,it is transmitted to the computer through serial communication.A low frequency magnetic field probe operating at 10 kHz to 10 MHz and a high frequency magnetic field probe operating at 10 MHz to 300 MHz were developed.The low-frequency magnetic field probe consists of a 50-turn winding coil,an integration circuit,a detection circuit,and a single-chip circuit.The coil converts the magnetic field into a high-frequency voltage signal according to the law of electromagnetic induction,and the frequency response is 20dB/10 octave;The frequency response slope of the integration circuit is-20dB/10 times,which can amplify and compensate the coil input signal,so that the frequency response flatness of the output signal does not exceed 4dB;The detection circuit detects the input signal of the integration circuit and converts it into a DC voltage output;the single-chip circuit performs analog-to-digital conversion on the DC voltage signal input by the detection circuit,and the data is stored.After the measurement is completed,the data is exported by communicating with the computer.The high-frequency magnetic field probe consists of a single-twist winding coil,a detection circuit,and a single-chip circuit.Due to the higher frequency,the coil output signal can be detected by the detector circuit without using an integrating circuit.The low frequency magnetic field probe has a working frequency of 10 kHz to 10 MHz,and the magnetic field range that can be measured is 0.005 A/m to 100 A/m,and the dynamic range is 85 dB.The high-frequency magnetic field probe has an operating frequency of 10MHz~300MHz,and the magnetic field range that can be measured is 0.002A/m~4A/m,and the dynamic range is 68 dB.The overall size of the magnetic field probe is 22 mm × 24 mm × 55 mm.