Soil moisture is closely related to the occurrence frequency and the time of landslides disasters, precisely in situ measurement for soil moisture becomes quite critical. The electrodes of conventional dielectric sensor for soil moisture are fragile, large, and unsuitable for integration. Interdigital (IDT) fringing-field capacitive sensors based on printed circuit board (PCB) technology can be used for noncontact measurement and small-scale packaging. In this article, to optimize the sensitivity and penetration depth of the IDT capacitive sensor with a fixed electrode contour area, the influences of IDT fingers shape and size on the sensitivity and penetration depth are discussed in a wide range by using equivalent capacitance theory. Then, the special working cases are intuitively and accurately analyzed by using the finite element analysis (FEA) method. The results show that the sensor with more electrode fingers and smaller finger gap has high sensitivity, yet has a thinner penetration depth, and it requires a tradeoff between sensitivity and penetration depth in practical applications. In addition, the performance of regular and circular IDT sensors with the same specifications is basically identical, and the circular IDT sensor has a slightly better accuracy. Finally, the proposed IDT sensors with different electrode specifications as well as the associated signal conditioning circuit are fabricated and calibrated to verify the theoretical and simulation results. The performance of the designed sensor was compared with other commercial sensors based on the thermogravimetric method. The experimental results meet the expected requirements well, with a repeatability correlation coefficient of $R^{2} \,\,=0.992$ and a mean square error of 0.01089.

There are many problems in traditional manual inspection, such as poor real-time performance, complex operation and large environmental impact on monitoring results when using ultrasonic and ultra high frequency (UHF) inspection methods. In order to realize online monitoring of partial discharge (PD) in high-voltage switchgears, a live display capacitance sensor equipped with high-voltage switchgear is proposed to acquire discharge pulse and monitor the discharge information of switchgear in real time. With the technology of FPGA, the sampling frequency of 50MHz is used to collect one million data points in 10 milliseconds and a half cycle. Hanning window function data processing technology and fast Fourier transform (FFT) technology are used to obtain the high frequency discharge spectrum of the internal ports and insulators of high-voltage switchgear cabinet, thus realizing the online monitoring of PD, and greatly reducing the cost of the monitoring circuit. It is convenient for popularization and application, and meets the online monitoring requirements of PD through practical tests.

Soil moisture content plays a crucial role in precision agriculture and geological hazard monitoring, driving the need for stable, reliable, and high-precision sensors. Capacitive soil moisture sensors based on Frequency Domain Reflectometry (FDR) are widely adopted due to their favorable measurement performance, yet their accuracy is highly susceptible to environmental interferences such as temperature, salinity (electrical conductivity), and soil type. This paper systematically reviews current calibration strategies addressing these three factors, classifying them into hardware-based compensation and software-based calibration (including conventional mathematical and machine learning models). Furthermore, it critically analyzes the trade-offs of these approaches in terms of robustness, scalability, and field applicability. To break through current technical limitations, this review argues that future research must prioritize the physical decoupling of multi-parameter interferences under extreme conditions. Additionally, to overcome the generalization crisis of current data-driven models, adaptive strategies utilizing techniques like transfer learning are essential. Finally, implementing Edge-AI on resource-constrained hardware is crucial for achieving calibration-free or real-time online calibration strategies, ensuring long-term measurement accuracy.

Magnetic resonant wireless power transfer (MR-WPT) has several advantages over conventional wired underground power supply methods. However, MR-WPT inevitably encounters metal conductors, which reduce the system efficiency through the eddy loss induced in the conductor by high-frequency electromagnetic waves. In this paper, the effect of resonant frequency variations caused by metal tube interference with the aim of maximizing the system efficiency is studied. According to the variation in the resonant frequency, the system efficiency is analytically derived by an equivalent circuit model. Electromagnetic simulations are carried out to further analyze the metal tube interference on the system. The results demonstrate the existence of an optimal resonant frequency that maximizes the system efficiency. Aluminum tube interference produces a lower optimal resonant frequency and higher efficiency than a 304 stainless-steel tube. When the metal tube is slotted, the optimal slot width and number of slots enhance the maximum efficiency and reduce the optimal resonant frequency and frequency drift. With slot widths of 2 and 8 mm, the system efficiency reaches ∼67% at 40.1 kHz and 55% at 48 kHz, respectively. Finally, different types of slotted tubes are fabricated, and the theoretical results are experimentally verified.

Supplying power for multi-load devices via magnetic resonance wireless power transfer (MR-WPT) has attracted extensive attention, but it also presents more challenging analysis for the system configuration. This study provides an optimization analysis of coil position considering the cross-coupling effect, thereby improving the performance of a dual-receiver MR-WPT system with dynamic transmitting coil (Tx-coil) position. First, the expression of the overall power transfer efficiency (PTE) and the optimal load are derived using equivalent circuit model (ECM), and a comparative discussion of the system characteristics with and without cross-coupling is carried out. It shows that the PTE reaches the peak at the resonant frequency of each receiver (Rx) rather than at that of the transmitter, and the PTE decreases and optimal load increases after considering cross coupling at a short transfer distance. Then the relationship between the coil position and PTE under cross-coupling is discussed, it proves the existence of an optimal transfer distance to achieve the maximum PTE for the symmetric Rxs system, and the dynamic Tx system has an optimal movement range of Tx-coil at the optimal load, so that the system can obtain stable and efficient power transfer when the Tx-coil moves within this range. Finally, the theoretical results are verified through experiments in the lab. Under the optimal operation, an overall efficiency above 75% can be achieved for a system when the Tx-coil moves within this range that the gap of receivers at 100mm.

This letter aims to provide an analysis of selecting the optimal coil position under a dynamic transmitting coil (Tx-coil) to improve the performance of a dual-receiver magnetic resonance wireless power transfer (MR-WPT) system. The expressions of power transfer efficiency (PTE) and optimal load are derived using equivalent circuit model (ECM), and the relationship between coils position and PTE under cross-coupling is discussed; it proves the existence of an optimal transfer distance to achieve the maximum PTE for a symmetric receivers (Rxs) system. The system has a dynamic Tx-coil position variation range under optimal load of maintaining stable and efficient power transfer when the Tx-coil moves within this range. Finally, the theoretical results are verified through experiments in the laboratory. Under the optimal operation, a stable overall efficiency above 75% can be achieved for a system when the Tx-coil moves within this range that the gap of receivers at 100 mm.