Expendable current profiler (XCP) is one of the most vital devices detecting ocean currents. Compared with other methods, the expendable feature makes trials with XCP much faster and more hidden, while the accuracy of XCP is considerably influenced by electromagnetic noise all around. Aiming at researching the influence and reducing the noise, this study carried out laboratory simulation experiments. The designed laboratory experiments mainly have a self-developed rotation gear, an XCP prototype, a plastic flume, and two copper plates as power. Firstly, these experiments analyzed the main sources of electromagnetic noise for XCP detection. Secondly, we built a noise simulation environment and conducted XCP detection experiments under different noise in the flume. The data obtained by XCP were transmitted to the computer to be stored and processed. The results show the internal noise impact on XCP is significantly less than the external. For an excitation power of 1 mV, the offset of theoretical and actual data brought by internal noise is 12 times smaller than external and can be corrected.

This paper presents a compact, high-efficiency electromagnetic transmitter for Controlled-source Audio-frequency Magnetotelluric (CSAMT) applications, operating in the 10–100 kHz range. A novel bipolar square-wave inverter topology is proposed, which directly modulates the transformer’s secondary-side AC output, eliminating conventional rectification and filtering stages. This design reduces system losses (simulated efficiency > 90%) and achieves an approximately 40% reduction in both volume and weight. The power stage uses a full-bridge bipolar inverter topology with SiC-MOSFETs, combined with a high-frequency transformer for voltage gain. Simulation, laboratory testing, and EMI evaluation confirm stable square-wave generation and full compliance with EN55032 Class A standards. Field validation with a CSAMT receiver demonstrates effective signal transmission and high-resolution subsurface imaging, thereby improving the efficiency and portability of urban geophysical exploration.

Electrical resistivity tomography (ERT) is an important method for exploring oil and gas formations, mineral deposits, and groundwater resources. However, most ERT instruments have limitations such as complicated human–computer interaction, few measurement parameters, difficulties in remote monitoring, and lack of four-dimensional (4D) exploration functions. To overcome these limitations, in this study we proposed and developed software for a remote control 4D ERT system based on a cloud platform and Internet of Things (IoT) technology. Specifically, acquisition device control, channel and control, acquisition control, and remote monitoring systems were designed, with various modules being debugged and optimized multiple times. The system is equipped with a 4G module, through which the collected data are transmitted to the cloud platform to realize real-time, stable, and long-distance data acquisition and transmission. Furthermore, the system realizes remote monitoring, real-time measurement, and other functions via the cloud and IoT technology, thereby providing strong technical support for achieving 4D exploration. The developed system was empirically evaluated by applying it to explore the Gequ Landslide area in Jainca County, Qinghai Province, China. The exploration results indicate that the system software has stable functions and high intelligence; thus it satisfies the requirements for field exploration.

To enhance the resolution of shallow geological structure detection, this study developed a Controlled-Source wide frequency range Magnetotelluric Detector (called CSUMT) with a frequency range spanning from 1 Hz to 1 MHz, and conducted systematic field experiments in Fengxian County, Shaanxi Province. The CSUMT system employs a high-precision 24-bit analog-to-digital converter and is compatible with both inductive magnetic sensors and superconducting quantum interference device (SQUID) magnetic sensors, featuring wide bandwidth and high dynamic range. Comparative experiments with the commercial V8 instrument demonstrated high consistency in electric field, magnetic field, and apparent resistivity measurements, confirming the CSUMT system’s reliability in field applications. In addition, this study compared the performance of inductive and SQUID magnetic sensors in actual surveys, revealing that SQUID sensors exhibit lower noise and more stable data output, making them suitable for signal detection across a broader frequency range. The results validate the practicality of the CSUMT system in complex geological environments and provide experimental support for the appropriate selection of magnetic sensors.

Although high-frequency electromagnetic methods, such as Radio Magnetotellurics (RMT) and Controlled-Source Radio Magnetotellurics (CSRMT), are highly effective for shallow-to-medium depth exploration, deploying traditional transmitter–receiver setups remains labor-intensive and significantly slows down large-scale surveys. To overcome these logistical bottlenecks, we developed a mobile Ultra-Audio Frequency Electromagnetic (UAEM) measurement system. While the hardware is designed with dual-mode capabilities supporting conventional controlled-source operations, this paper specifically focuses on its application in a Signals of Opportunity (SOOP) mode. By utilizing pre-existing, stable anthropogenic signals, including Amplitude Modulation (AM) broadcasts and naval very low frequency communications, the system effectively functions as a broadband RMT receiver. Technical evaluations demonstrate that the instrument operates across a 1 Hz to 1000 kHz bandwidth with a high sampling rate of 2.5 MHz. Furthermore, it achieves a dynamic range of 143 dB and maintains an apparent resistivity measurement accuracy of better than 3%. Thanks to its modular, vehicle-towed design, the UAEM system enables continuous, on-the-move data acquisition wherever ambient field sources are available. This approach eliminates the need for dedicated transmitter deployment, fundamentally reducing exploration costs and boosting overall survey efficiency.

Electrical and seismic exploration are two widely used geophysical methods in geological surveys. They reflect different geophysical properties of underground rocks, but each method can only provide information from a single perspective of the rock structure’s physical parameters. As a result, relying on a single geophysical method can lead to ambiguous interpretations. To address this issue, this paper presents the development of a multi-functional, high-power, multi-channel, rolling, fast measurement system for combined electrical and seismic exploration. The system features the following capabilities: it can be used simultaneously for both electrical and seismic exploration; it supports high-power operation, with a transmission power of up to 10 kW during electrical exploration; it includes multiple measurement channels for rolling measurement and data acquisition, with a sampling rate of up to 100 ksps, significantly improving work efficiency and expanding the frequency range. The distance between channels can be selected from 1 to 20 m, greatly enhancing the system’s adaptability to various environments. Additionally, we have designed accompanying upper-level software that not only stores data internally but also displays waveforms in real-time on a computer for monitoring and control. The experimental results demonstrate that the instrument operates stably and meets the requirements for field exploration.