# Gradient-Type Magnetoelectric Current Sensor with Strong Multisource Noise Suppression

^{1}

^{2}

^{*}

## Abstract

**:**

## 1. Introduction

## 2. Configuration, Structure, and Prototype

^{2}hole area). The sensor is symmetrically mounted and loosely contacted with the foamed rubber in the plastic box as in Figure 1c. The usage of copper screen is to minimize the influence of ambient electric field noises based on the conductive shielding effect, and to reduce the magnetic field attenuation due to eddy current effect by reducing effective eddy current vortexes. To enable the MFG-induced ME effect for current measurement, the two ME composites are prepared by bonding a layer of PZT (Pb(Zr, Ti)O

_{3}, Ceram-Tec P8) piezoelectric ceramic plate of 12 mm length, 6 mm width, and 1 mm thickness between two layers of [112]-textured Terfenol-D (Tb

_{0.3}Dy

_{0.7}Fe

_{1.92}, Baotou Rare Earth, Baotou, China) magnetostrictive alloy plates of the same dimensions, by cutting the ME composite along its length direction (3-) using dicing saw (DAD 321, Giorgio Technology, Mesa, AZ, USA) with lowest blade feeding speed of 0.2 mm/s, blade depth of 3 mm, and by separating the obtained ME composites with dimensions of 12 mm long, 3 mm wide, and 1 mm thick. The bias magnets are made of NdFeB (N55M, V-magnet, Shanghai, China) with dimensions of 6 mm long, 3 mm wide, and 2 mm thick. As in Figure 1b, the magnetization (M) direction of the Terfenol-D plates and the polarization (P) direction of the PZT plate are oriented in their length (3-) and thickness (1-) directions, respectively. The negative electrode surfaces of the PZT plate in the two ME composites are electrically connected together to form a back-to-back capacitor configuration, while the positive electrode surfaces of the first and second PZT plates are connected to the signal core and ground shield of the coaxial cable with BNC termination, respectively. Therefore, the output voltage is directly obtained from the ME composites pair, and is directly calibrated against current amplitude to give the current sensitivity characterized by a unit output voltage per unit ampere in the cable.

## 3. Working Principle

#### 3.1. Current Sensing Based on MFG Detection and Conversion

#### 3.2. Coupling and Suppression of Multsource Noises

## 4. Performance Evaluation, Results, and Discussion

#### 4.1. Intrincsic Performance

#### 4.1.1. Evaluation of Voltage Coefficient of MFG-Induced ME Effect

#### 4.1.2. Calibration of Current Sensitivity

^{®}SR865, Sunnyvale, CA, USA), by converting and amplifying the AC reference voltage into the corresponding AC current using a current supply amplifier (AE Techron

^{®}7548, Elkhart, IN, USA), by driving the cable with the AC current of 0–20 A in steps of 0.5 A, by measuring ${V}_{G}$ using the lock-in amplifier, and by calculating the slope of ${V}_{G}\u2013I$ curves at each frequency. The AC current was monitored and assured using a current probe (HIOKI

^{®}9273, Nagano, Japan) and a signal conditioner (HIOKI

^{®}3271) connected to the current feedback input of the lock-in amplifier. An average of non-resonance ${S}_{I}$ of 0.62 mV/A is achieved over a broad frequency range of 1 Hz–80 kHz, while high resonance ${S}_{I}$ of 8.4 mV/A is obtained at ${f}_{\mathrm{r}}$ of 120 kHz. The similarity trends in Figure 3a and Figure 4a implicit a linear relationship between current-induced MFG effect and the MFG-induced ME effect as described by Equations (4) and (6).

#### 4.1.3. Evaluation of Equivlent Current Noise Density

#### 4.2. Extrincsic Performance

#### 4.2.1. Evaluation of Thermal Stability

^{®}, Guangzhou, China), with two via holes on the top and bottom covers to enable the straight current carrying cable pass through the oven. By controlling the temperature slowly increase from 18 °C to 65 °C with step of 5 °C and 10 min holding time to ensure thermal equilibrium state of the system, the ${S}_{I}$ at each temperature is obtained using the method described in Section 4.1.2. We see from Figure 6 that an increasing trend of ${S}_{I}$ as function of T can be found within 18–65 °C. The ${S}_{I}$. approximately linearly increases in the temperature range of 18–65 °C, while it decreases when T > 50 °C. The curve is in agreement with previous studies on thermal stability of ME composites, and may explained by increasing trend in temperature-dependent piezoelectric charge coefficients of PZT-8 plates and the soften effects of epoxy hardener at higher temperatures [28]. In detail, at low temperature range (18–50 °C), the rapid increasing trend of ${S}_{I}$ can be attributed to piezoelectric charge coefficient of PZT-8 plates. However, when temperature continues to increase (T > 50 °C), the epoxy becomes soft and consequently weakens the mechanical coupling between Terfenol-D plates and PZT-8 plates, resulting in the slow increase of ${S}_{I}$ as function of T. An overall relative sensitivity drift of <0.2%/°C is achieved in the temperature range of 18–65 °C.

#### 4.2.2. Evaluation of Magnetic Fields Noise

^{®}7548, Elkhart, IN, USA) connected to an arbitrary waveform generator (Agilent

^{®}33210A, Santa Clara, CA, USA), by monitoring the current in the coil with a current probe (HIOKI

^{®}9273, Nagano, Japan) and it signal conditioner (HIOKI

^{®}3271, Nagano, Japan), and by recording ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ using an oscilloscope (Tektronix

^{®}MSO2014, OR, USA). Results in Figure 7a indicate that the 50 Hz component of ${\tilde{v}}_{\mathrm{M},\mathrm{A}}$ and ${\tilde{v}}_{\mathrm{M},\mathrm{B}}$ are of same amplitude of 1.5 mV, while the 50 Hz component of ${\tilde{v}}_{G}$ in ${V}_{G}$ is 0.2 mV. The ${\tilde{v}}_{G}$ in ${V}_{G}$ is evaluated to be 7 times smaller than ${v}_{\tilde{B}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, corresponding to a CMRR of 17 dB in a $\tilde{B}$ interfered environment arising from ambient power cables. Results in Figure 7b are obtained by exciting the Helmholtz coil using pulse width-modulated current signal with pulse width of 10 $\mathsf{\mu}\mathrm{s}$, rising edge of 40 ns, and period of 20 ms in analogous to possible discharge current-induced $\tilde{B}$. Waveforms in Figure 7b indicate that the peak value of ${\tilde{v}}_{\mathrm{M},\mathrm{A}}$ and ${\tilde{v}}_{\mathrm{M},\mathrm{B}}$ are of same amplitude of 5 mV, while the suppressed peak value of ${\tilde{v}}_{G}$ in ${V}_{G}$ waveforms is less than 0.2 mV. The ${\tilde{v}}_{G}$ in ${V}_{\mathrm{G}}$ is evaluated to be 12 times smaller than ${v}_{\tilde{B}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, corresponding to a CMRR of 28 dB. The larger CMRR in this case can be explained by high frequency component in the pulse signal and high ${\alpha}_{G}$ in Figure 3a. The zero-crossing waveforms in Figure 7b can be explained by eddy current effects and magnetostrictive effects in Terfenol-D plates. Results in Figure 7c are obtained by exciting the Helmholtz coil using square wave current signal with period of 20 ms and rising edge of 0.1 ms in analogous to possible $\tilde{B}$ induced by pulse-width modulated actuator in the electrical system. Results in Figure 7c have similar trends to those in Figure 7b, except for the larger transition time at the edge of square wave, which can be explained by the parasitic capacitance, eddy current effects, and magnetostrictive effects in Terfenol-D plates. The ${\tilde{v}}_{G}$ in ${V}_{G}$ is evaluated to be 12 times smaller than ${v}_{\tilde{B}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, corresponding to a CMRR of 21 dB.

#### 4.2.3. Evaluation of Electric Field Noise

^{®}7548, Elkhart, IN, USA) connected to an arbitrary waveform generator (Agilent

^{®}33210A, Santa Clara, CA, USA), and by recording ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$,and ${V}_{G}$ using an oscilloscope (Tektronix

^{®}MSO2014, Beaverton, OR, USA). The two coppers plates both have width, length, and thickness of 100 mm, 100 mm, and 1 mm, respectively. Figure 8a shows the waveforms of ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ when the excitation voltage is sine wave with amplitude of 50 V ($\left|\tilde{E}\right|=1000\mathrm{V}/\mathrm{m}$). Figure 8a suggest that 50 Hz components of ${v}_{\tilde{E}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$ amplitudes are approximately 2.1 mV, while the 50 Hz component of ${\tilde{v}}_{G}$ in ${V}_{G}$ is 0.18 mV. The ${\tilde{v}}_{G}$ in ${V}_{G}$ is evaluated to be 11 times smaller than ${v}_{\tilde{E}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, and the CMRR is evaluated to be 21 dB without the copper screen shielding. Figure 8b shows the $\tilde{E}$-induced waveforms of ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ when the copper plates are driven by pulse width-modulated voltage signal with pulse width of 10 $\mathsf{\mu}\mathrm{s}$, rising edge of 40 ns, and period of 20 ms in analogous to possible, voltage-induced $\tilde{E}$ raising from the ON/OFF action of the electrical system. Figure 8b suggests that the peak values of ${v}_{\tilde{E}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$ are approximately 5 mV, while peak values of ${\tilde{v}}_{G}$ in ${V}_{G}$ are 0.7 mV. The ${\tilde{v}}_{G}$ in ${V}_{G}$ is evaluated to be 7 times smaller than ${v}_{\tilde{E}}$. in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, and the CMRR is evaluated to be 17 dB without the copper screen shielding. Figure 8c shows the $\tilde{E}$-induced waveforms of ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ when the copper plates are driven by square voltage signal at 50 Hz. Figure 8c suggests that the peak values of ${v}_{\tilde{E}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$ are approximately 5.8 mV, while peak values of ${\tilde{v}}_{G}$ in ${V}_{G}$ are 0.8 mV. The ${\tilde{v}}_{G}$ in ${V}_{G}$ is evaluated to be 7.2 times smaller than ${v}_{\tilde{E}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$, and the CMRR is evaluated to be 17 dB without the copper screen shielding.

#### 4.2.4. Evaluation of Vibration Noise

^{®}5948, Norwood, MA, USA); by controlling the head to move in triangular wave form with period of 0.64 s and amplitude of 5 mm to a square wave form of velocity with amplitude of 15.6 mm/s and period of 0.64 s, and pulsed acceleration with peak value of 18.35 $\mathrm{m}/{\mathrm{s}}^{2}$ with period of 0.32 s; and by recording ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ using an oscilloscope (Tektronix

^{®}MSO2014, Beaverton, OR, USA). Results in Figure 9 indicate that a pulsed $\tilde{a}$ with $\left|\tilde{a}\right|=18.35\mathrm{m}/{\mathrm{s}}^{2}$ will raise ${v}_{\tilde{a}}$ in ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$ up to 4.3 mV in conventional strength-type ME current sensor; however, ${v}_{a}$ in ${V}_{G}$ is more than 8 times reduced to 0.49 mV based on the MFG-induced ME effect in the gradient-type current sensor. The CMRR is evaluated to be 18 dB in the present case. A little difference between waveforms of ${V}_{\mathrm{M},\mathrm{A}}$ and ${V}_{\mathrm{M},\mathrm{B}}$ can be found in Figure 9, which may be caused by difference in mode shape asymmetry of the holder. However, it is safe to say that the CMRR will be much higher in the moving train sets of HSR system, since larger platforms vibrate more evenly, resulting in smaller acceleration difference at each ME composite.

## 5. Suppression of Multisource Noises

#### 5.1. Experiment Setup

#### 5.2. Results and Discussion

## 5. Conclusions

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

- Ripka, P. Electric current sensors: A review. Meas. Sci. Technol.
**2010**, 21, 1–23. [Google Scholar] [CrossRef] - Morello, R.; Mukhopadhyay, S.; Liu, Z.; Slomovitz, D.; Samantaray, S. Advances on sensing technologies for smart cities and power grids: A Review. IEEE Sens. J.
**2017**, 17, 7596–7610. [Google Scholar] [CrossRef] - Xiao, C.C.; Zhao, L.Y.; Asada, T.; Odendaal, W.; Van Wyk, J. An overview of integratable current sensor technologies. In Proceedings of the 38th IAS Annual Meeting, Industry Applications Conference 2003, Salt Lake City, UT, USA, 12–16 October 2003; pp. 1251–1258. [Google Scholar]
- Shaukat, N.; Khan, B.; Ali, S.; Mehmood, C.; Khan, J.; Farid, U.; Majid, M.; Anwar, S.M.; Jawad, M.; Ullah, Z. A survey on electric vehicle transportation within smart grid system. Renew. Sustain. Energy Rev.
**2017**, 81, 1329–1349. [Google Scholar] [CrossRef] - Varaiya, P. Smart cars on smart roads: Problems of control. IEEE Trans. Autom. Control
**1993**, 38, 195–207. [Google Scholar] [CrossRef] - Hsi, P.H.; Chen, S.L. Electric load estimation techniques for high-speed railway (HSR) traction power systems. IEEE Trans. Veh. Technol.
**2001**, 50, 1260–1266. [Google Scholar] - Ziegler, S.; Woodward, R.C.; Iu, H.H.C.; Borle, L.J. Current sensing techniques: A review. IEEE Sens. J.
**2009**, 9, 354–376. [Google Scholar] [CrossRef] - Sun, X.H.; Huang, Q.; Jiang, L.J.; Pong, P.W. Overhead high-voltage transmission-line current monitoring by magnetoresistive sensors and current source reconstruction at transmission tower. IEEE Trans. Magn.
**2014**, 50, 1–5. [Google Scholar] [CrossRef] [Green Version] - Leung, C.M.; Or, S.W.; Ho, S.L.; Lee, K.Y. Wireless condition monitoring of train traction systems using magnetoelectric passive current sensors. IEEE Sens. J.
**2014**, 14, 4305–4314. [Google Scholar] [CrossRef] - Samimi, M.H.; Mahari, A.; Farahnakian, M.A. The Rogowski coil principles and applications: A review. IEEE Sens. J.
**2015**, 15, 651–658. [Google Scholar] [CrossRef] - Ward, D.A.; Exon, J.L.T. Using Rogowski coils for transient current measurements. Eng. Sci. Educ. J.
**1993**, 2, 105–113. [Google Scholar] [CrossRef] - Dupraz, J.; Fanget, A.; Grieshaber, W.; Montillet, G. Rogowski coil: Exceptional current measurement tool for almost any application. In Proceedings of the IEEE Power Engineering Society General Meeting 2007, Tampa, FL, USA, 24–28 June 2007; pp. 1–8. [Google Scholar]
- McNeill, N.; Gupta, N.K.; Burrow, S.G.; Holliday, D.; Mellor, P.H. Application of reset voltage feedback for droop minimization in the unidirectional current pulse transformer. IEEE Trans. Power Electron.
**2008**, 23, 591–599. [Google Scholar] [CrossRef] - McNeill, N.; Gupta, N.K.; Armstrong, W.G. Active current transformer circuits for low distortion sensing in switched mode power converters. IEEE Trans. Power Electron.
**2004**, 19, 908–917. [Google Scholar] [CrossRef] - Román, M.; Velasco, G.; Conesa, A.; Jeréz, F. Low consumption flux-gate transducer for AC and DC high-current measurement. In Proceedings of the IEEE Power Electronics Specialists Conference, Rhodes, Greece, 15–19 June 2008; pp. 535–540. [Google Scholar]
- Dezuari, O.; Belloy, E.; Gilbert, S.; Gijs, M. Printed circuit board integrated fluxgate sensor. Sens Actuators A Phys.
**2000**, 81, 200–203. [Google Scholar] [CrossRef] - Lenz, J.; Edelstein, S. Magnetic sensors and their applications. IEEE Sens. J.
**2006**, 6, 631–649. [Google Scholar] [CrossRef] - Open Loop Hall Effect Sensors. Available online: https://buy.fwbell.com/current-sensors/open-loop-hall-effect-sensors.html (accessed on 30 October 2017).
- Yang, X.; Li, Y.; Zheng, W.; Guo, W.; Wang, Y.; Yan, R. Design and realization of a novel compact fluxgate current sensor. IEEE Trans. Magn.
**2015**, 51, 1–4. [Google Scholar] [CrossRef] - Bichurin, M.; Petrov, R.; Leontiev, V.; Semenov, G.; Sokolov, O. Magnetoelectric current sensors. Sensors
**2017**, 17, 1271. [Google Scholar] [CrossRef] [PubMed] - Leung, C.M.; Or, S.W.; Zhang, S.Y.; Ho, S. Ring-type electric current sensor based on ring-shaped magnetoelectric laminate of epoxy-bonded Tb
_{0.3}Dy_{0.7}Fe_{1.92}short-fiber/NdFeB magnet magnetostrictive composite and Pb(Zr,Ti)O_{3}piezoelectric ceramic. J. Appl. Phys.**2010**, 107, 09D918. [Google Scholar] [CrossRef] - Ramboz, J.D.; Destefan, D.E.; Stant, R.S. The verification of Rogowski coil linearity from 200 A to greater than 100 kA using ratio methods. In Proceedings of the 19th IEEE Instrumentation and Measurement Technology Conference (IMTC/2002), Anchorage, AK, USA, 21–23 May 2002; pp. 687–692. [Google Scholar]
- Tipek, A.; O’Donnell, T.; Connell, A.; McCloskey, P.; O’Mathuna, S. PCB fluxgate current sensor with saturable inductor. Sens Actuators A Phys.
**2006**, 132, 21–24. [Google Scholar] [CrossRef] - Sun, C.; Wen, Y.; Li, P.; Ye, W.; Yang, J.; Qiu, J. Self-contained wireless Hall current sensor applied for two-wire zip-cords. IEEE Trans. Magn.
**2016**, 52, 1–4. [Google Scholar] [CrossRef] - Zhang, J.; Li, P.; Wen, Y.; He, W.; Yang, A.; Lu, C. High-resolution current sensor utilizing nanocrystalline alloy and magnetoelectric laminate composite. Rev. Sci. Instrum.
**2012**, 83, 115001. [Google Scholar] [CrossRef] [PubMed] - Eerenstein, W.; Mathur, N.; Scott, J.F. Multiferroic and magnetoelectric materials. Nature
**2006**, 442, 759–765. [Google Scholar] [CrossRef] [PubMed] - Nan, C.W.; Bichurin, M.I.; Dong, S.X.; Viehland, D.; Srinivasan, G. Multiferroic magnetoelectric composites: Historical perspective, status, and future directions. J. Appl. Phys.
**2008**, 103. [Google Scholar] [CrossRef] - Shen, Y.; Gao, J.; Wang, Y.; Li, J.; Viehland, D. Thermal stability of magnetoelectric sensors. Appl. Phys. Lett.
**2012**, 100, 173505. [Google Scholar] [CrossRef] - Dong, S.X.; Bai, J.G.; Zhai, J.; Li, J.F.; Lu, G.Q.; Viehland, D. Circumferential-mode, quasi-ring-type, magnetoelectric laminate composite-a highly sensitive electric current and/or vortex magnetic field sensor. Appl. Phys. Lett.
**2005**, 86, 182506. [Google Scholar] [CrossRef] - Zhang, M.; Or, S.W. Magnetoelectric transverse gradient sensor with high detection sensitivity and low gradient noise. Sensors
**2017**, 17, 2446. [Google Scholar] [CrossRef] [PubMed] - Wang, Y.J.; Gao, J.Q.; Li, M.H.; Shen, Y.; Hasanyan, D.; Li, J.F. A review on equivalent magnetic noise of magnetoelectric laminate sensors. Philos. Trans. R. Soc. A
**2014**, 372. [Google Scholar] [CrossRef] [PubMed]

**Figure 1.**The novel gradient-type ME current sensor based on the product effect of current-induced MFG effect and the MFG-induced ME effect: (

**a**) top-view of current sensor assembly configuration and magnetic fields (

**B**) and its gradient ($G$) generated in the vicinity of a current (I)-carrying cable (

**b**) structure of ME composites pair in the sensor, in which M denotes the magnetization direction of the magnetostrictive layers and P indicates the polarization direction of the piezoelectric layer; (

**c**) packaged prototype.

**Figure 2.**Ishikawa diagram of multisource noise coupling mechanism in the proposed gradient-type ME current sensor.

**Figure 3.**Frequency (f) dependence of: (

**a**) measured gradient-ME voltage coefficient ${\alpha}_{G}$ and its calculated results from FEM (${\alpha}_{G,\mathrm{FEA}}$); (

**b**) measured ME voltage coefficients of the two ME composites (${\alpha}_{\mathrm{V},\mathrm{A}}$ and ${\alpha}_{\mathrm{V},\mathrm{B}}$) and their difference (${\alpha}_{\mathrm{V},\mathrm{A}}-{\alpha}_{\mathrm{V},\mathrm{B}}$), together with that of the ME voltage coefficient calculated from FEA (${\alpha}_{\mathrm{FEA}}$).

**Figure 4.**(

**a**) Frequency (f) dependence of the measured current sensitivity (${S}_{I}$) when R = 8 mm, (

**b**) measured (symbols) and calculated (solid lines) $G$ and ${V}_{G}$ various current amplitude at 50 Hz, and (

**c**) measured (symbols) and calculated (solid lines) $G$ and ${S}_{I}$ at various R of 8–20 mm at 50 Hz.

**Figure 5.**(

**a**) Measured voltage noise density spectra of each ME composites (${u}_{\mathrm{A}}$ and ${u}_{\mathrm{B}}$), the current sensor (${u}_{G}$), and the lock-in amplifier noise floor (${u}_{\mathrm{Amp}}$), together with the calculated thermal noise density (${u}_{T}$) spectra. (

**b**) Measured (symbols) and fitted (solid lines) equivalent current noise density (i) spectra in a magnetically-unshielded laboratory environment at 20 °C without intentional interference.

**Figure 6.**Experiment results of thermal stability: temperature (T) dependence of current measurement sensitivity (${S}_{I}$).

**Figure 7.**Experimental results of ambient magnetic field noises ($\tilde{B}$)-induced voltage noises in ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ when $\tilde{B}$ is created by (

**a**) sine wave, (

**b**) pulse, and (

**c**) square wave current excitation, respectively.

**Figure 8.**Experimental results of ambient electric field noises: ($\tilde{E}$)-induced voltage noises in ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$ when $\tilde{E}$ is created by exciting (

**a**) sine wave, (

**b**) pulse width modulated, and (

**c**) square voltage signals on two copper plates, respectively. (The peak-value of $\left|\tilde{E}\right|$ is approximately 1000 V/m for all cases).

**Figure 9.**Experimental results of vibrational acceleration noises: ($\tilde{a}$)-induced voltage noises in ${V}_{\mathrm{M},\mathrm{A}}$, ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$.

**Figure 10.**Schematics diagram of experiment setup for multisource noise suppression performance evaluation. Labels, lines, and arrows with colors of magenta, brown, blue, green, and red represent $\tilde{B}$-, $\tilde{E}$-, $\tilde{a}$-, $I$, and T-related equipments, respectively.

**Figure 11.**Experiment system for multisource noise suppression performance evaluation. Labels with colors of magenta, brown, blue, green, and red represent $\tilde{B}$-, $\tilde{E}$-, $\tilde{a}$-, $I$-, and T-related equipment, respectively. (1. Vibration head; 2. Holder; 3. Cable; 4. Sensor; 5. Helmholtz coils; 6. Copper plates; 7. Vibration controller; 8. Convection oven; 9. Current probe amplifier; 10. Oscilloscope; 11. Lock-in amplifier; 12. Arbitrary waveform generator; 13. Constant-current supply amplifier; 14. Constant-voltage amplifier).

**Figure 12.**Experiment waveforms of ${V}_{\mathrm{M},\mathrm{A}}$and ${V}_{\mathrm{M},\mathrm{B}}$, and ${V}_{G}$, (green for raw data waveform, and black for 2-kHz low-pass filtered waveform) when measuring I in the cable under simultaneously interference of $\tilde{B}$, $\tilde{E}$, $\tilde{a}$, and thermal noises.

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Zhang, M.; Or, S.W.
Gradient-Type Magnetoelectric Current Sensor with Strong Multisource Noise Suppression. *Sensors* **2018**, *18*, 588.
https://doi.org/10.3390/s18020588

**AMA Style**

Zhang M, Or SW.
Gradient-Type Magnetoelectric Current Sensor with Strong Multisource Noise Suppression. *Sensors*. 2018; 18(2):588.
https://doi.org/10.3390/s18020588

**Chicago/Turabian Style**

Zhang, Mingji, and Siu Wing Or.
2018. "Gradient-Type Magnetoelectric Current Sensor with Strong Multisource Noise Suppression" *Sensors* 18, no. 2: 588.
https://doi.org/10.3390/s18020588