Instrumentation & Measurement Magazine 26-1 - 64

conductivity on the magnetic field gradually increases. This
decreases the measurement signal amplitude of the entire
measurement system.
Discussion and Conclusion
This paper proposes a method for seawater conductivity measurement
based on magnetic resonance coupling. The passive
transceiver coil is composed of a detection coil and a capacitive
element and measures the conductivity of the seawater. Since
the resonant component does not contain active or complex
circuit connections, it has advantages in space placement, installation
methods, and adaptability to the environment.
In the theoretical part, a circuit model of magnetic coupling
resonant system transmission in seawater is established
by equating seawater to seawater resistance and inductance.
In the experimental part, the measurement results obtained
at different resonance frequencies, with different frequency
deviations, and with four different topological structures at
different seawater conductivities are tested.
The following conclusions are drawn from this study.
◗ The current and voltage signals of the measurement
system change significantly with the shift in seawater
conductivity, and the sensitivity is higher at lower
conductivities.
◗ According to the measurement results obtained with
different frequency deviations, it is concluded that the
system has the best measurement performance at the resonant
frequency, and the frequency deviation will reduce
the measurement sensitivity. However, the measurement
system is very tolerant of frequency deviation.
◗ For the four different topological structures, the current
signals of the P-P and P-S structures show an upwards
trend with increasing conductivity, which is opposite to
those of the S-S and S-P structures. From the perspective
of the current signal, when the conductivity changes,
the response characteristics of the P-P and P-S structures
improve. From the perspective of the voltage signal,
when the conductivity changes, the response characteristics
of the S-S and S-P structures improve.
◗ As can be seen from the measured data at resonant
frequencies of 228 kHz, 338 kHz and 413.5 kHz, as the
resonant frequency increases, the drop in signal amplitude
ratio gradually increases, and the increase will
facilitate the differentiation of seawater conductivity.
The increase in resonance frequency will therefore
help to improve the resolution of seawater conductivity
measurements.
References
[1] X. Huang, R. W. Pascal, K. Chamberlain, C. J. Banks, M. Mowlemm,
and H. Morgan, " A miniature, high precision conductivity and
temperature sensor system for ocean monitoring, " IEEE Sensors J.,
vol. 11, no. 12, pp. 3246-3252, Dec. 2011.
[2] C. Thirstrup and L. Deleebeeck, " Review on electrolytic
conductivity sensors, " IEEE Trans. Instrum. Meas., vol. 70, pp.
1-22, 2021.
64
[3] S. Wu et al., " Investigation of the performance of an inductive
seawater conductivity sensor, " Sensors and Transducers, vol. 186,
no. 3, pp. 43-48, 2015.
[4] G. J. A. M. Brom-Verheijden, M. H. Goedbloed, and M. A. G.
Zevenbergen, " A microfabricated 4-electrode conductivity sensor
with enhanced range, " Proceedings. vol. 2, no. 13, 2018.
[5] B. A. Mazzeo and A. J. Flewitt, " Two-and four-electrode, widebandwidth,
dielectric spectrometer for conductive liquids: theory,
limitations, and experiment, " J. App. Phys., vol. 102, no. 10, 2007
[6] S. Wu et al., " Investigation of the performance of an inductive
seawater conductivity sensor, " Sensors and Transducers, vol. 186,
no. 3, pp. 43-48, 2015.
[7] N. Hamim et al., " Certified reference materials for calibration of
conductivity meter at the measuring of electrolytic conductivity
in water: preparation and its measurement, " AIP Conf. Proc., vol.
2175, no. 1, 2019.
[8] A. Kurs et al., " Wireless power transfer via strongly coupled
magnetic resonances, " Science Mag., vol. 317, pp. 83-86, 2007.
[9] I. Awai, Y. Sawahara, and T. Ishizaki, " Choice of resonators for a
WPT system in lossy materials, " in Proc. 2014 IEEE Wireless Power
Transfer Conf., pp. 106-109, 2014.
[10] H. Xiong and Y. Dong, " Non-contact measurement of electrolyte
solution with a passive coil placed in inductive coupling system, "
IEEE Sensors J., vol. 16, no. 11, pp. 4238-4245, Jun. 2016.
[11] G. Wei, X. Jin, C. Wang, J. Feng, C. Zhu, and M. I. Matveevich,
" An automatic coil design method with modified ac resistance
evaluation for achieving maximum coil-coil efficiency in WPT
systems, " IEEE Trans. Power Electron., vol. 35, no. 6, pp. 6114-6126,
Jun. 2020.
Ning Liu has been a Researcher of the National Ocean Technology
Center in Tianjin, China since 2019. His main research
directions are marine sensor measurement technology, underwater
digital communication technology and development of
expendable instruments. He received the Ph.D. degree from
Tianjin University in 2006. From 2006 to 2008, he worked in the
postdoctoral workstation of the National Ocean Technology
Center. After leaving the station, he worked in the National Marine
Technology Center and was engaged in the research of rapid
measurement technology of marine environmental parameters.
Yuanjie Miao (miaoyuanjie19@mails.ucas.ac.cn ) is a Student
at the National Ocean Technology Center in Tianjin, China. He
received the bachelor's degree from Anhui University in 2019.
His research interest is wireless transmission of magnetic coupling
resonance system.
Tao Wang is a Student at the National Ocean Technology Center
in Tianjin, China. He received the bachelor's degree from
Tianjin University in 2020. His research interest is wireless
transmission of magnetic coupling resonance system.
Yuhua Wu received the master degree from the National Ocean
Technology Center in Tianjin, China in 2005. His main research
directions are marine sensor measurement technology and development
of expendable instruments.
IEEE Instrumentation & Measurement Magazine
February 2023
Instrumentation & Measurement Magazine 26-1

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