Ultrasensitive Modulated Magnetoelectric Sensors and Low-Noise Readout Circuits for DC and Very Low-Frequency Weak Magnetic Signal Detection

In this work, the performance of a novel modulated magnetoelectric (ME) weak magnetic sensors with ultrahigh sensitivity, extremely weak dc, and very low-frequency magnetic signal detection capacity is discussed. The principle of a nonlinear modulated reading circuit suitable for ME sensors was introduced for the portable application of the modulated ME sensors. Moreover, a small low-noise modulated reading circuit was proposed. The ME sensor was composed of the ME sensing unit of the multi-push–pull structure and the low-noise modulated reading circuit. From the acquired experimental results, it was demonstrated that the equivalent magnetic field noise of the sensor reached 430 pT/ $\surd $ Hz @0.1 Hz, 148 pT/ $\surd $ Hz @1 Hz, 125 pT/ $\surd $ Hz @3 Hz, and 95 pT/ $\surd $ Hz @10 Hz, which coincided with the low-frequency magnetic field detection limit of the ME sensor unit. In addition, the minimum resolution of the dc field of the ME sensor was 1 nT. Moreover, the low-noise readout circuit size was only $24\times16$ mm with a power consumption of 178 mW and a bandwidth of dc-to-100 Hz. The proposed circuit can be used to replace commercial lock-in amplifiers of modulated ME sensors due to its simple structure and low price. This low-power miniaturized low-noise readout circuit and modulated ME sensor has excellent prospects in portable, multichannel, and high-volume industrial applications.