A Distributed Phase Measurement Method of Frequency-Domain Electromagnetic Detection

A distributed phase measurement method of frequency-domain electromagnetic detection is proposed. The theoretical analysis of the previous literature shows that in electromagnetic detection applications, phase as an independent measurement parameter can reduce the diversity of solution, and it also has the advantage of greater steepness than the amplitude. Currently, there are few literature dealing with the phase in the practical application of audio electromagnetic detection, because it is difficult to obtain the phase from the separated devices. A synchronization recording system is designed based on the most widely used GPS and fiducial timestamp (FIDTS) technology. The phase errors caused by FIDTS, hardware circuit noise, and FFT spectrum leakage are analyzed. In addition, the synchronization data lost by GPS can be supplemented by interpolation. To prove the effectiveness of the method, a test platform was built in the laboratory. System test results show that the synchronization error between any two systems is less than 48 ns, and the phase error is less than 0.173° at 10 kHz. The experimental result of abnormal loop shows that the phase is more accurate than the amplitude.