In this paper, a dc current source dedicated to four-probe low-frequency noise measurements is presented. An output impedance value of 3 MΩ with a maximum output current of 1.5 mA was achieved. The white noise level of the current source was measured to be 4 x 10⁻²³ A²· Hz⁻¹ with a corner frequency of 30 Hz. Thanks to its quasi-ideal behavior in terms of noise level and high output impedance value, this current source can be used to measure the intrinsic noise of materials using four-point measurements without any experimental or analytical corrections.

For an iron-chromium redox flow battery (ICRFB), sulfonated poly(ether ether ketone) (SPEEK) membranes with five various degrees of sulfonation (DSs) are studied. To select the SPEEK membrane with the ideal DS for ICRFB applications, the physicochemical characteristics and single-cell performance are taken into consideration. Following all the investigations, it has been determined that the SPEEK membrane, which has a DS of 57% and a thin thickness of 25 μm, is the best option for replacing commercial Nafion 212 in ICRFB. Firstly, it exhibits a better cell performance according to energy efficiency (EE) and coulombic efficiency (CE) at the current density range between 40 mA cm⁻² and 80 mA cm⁻². Additionally, it has a more stable EE (79.25–81.64%) and lower discharge capacity decay rate (50%) than the Nafion 212 (EE: 76.74–81.45%, discharge capacity decay: 76%) after 50 charge–discharge cycles, which proves its better oxidation stability as well. In addition, the longer self-discharge time during the open-circuit voltage test further demonstrates that this SPEEK membrane could be employed for large-scale ICRFB applications.

Pressure sensor used in marine hydrographic survey is an important device for the deep sea detection, the tsunami forecast and the marine engineering. Owing to its mature technology process and low production cost, silicon piezoresistive sensor is widely applied in the field of industrial pressure measurement. However, its temperature effect can result in non-negligible dynamic error, which cannot meet requirement of deep sea environment. The silicon-on-sapphire pressure sensor based on stress cup structure is presented. The output voltage values show a high deviation in the range of −6∼50°C due to temperature drift. In order to minimise this temperature effect, a temperature compensation algorithm is proposed to realise 0.03% accuracy in the full scale 60 MPa range. Compared with a reference commercial sensor in deep sea experiment, the test pressure sensors exhibit minor error, excellent similarity and coherence. This numerical method provides a new research direction for environmental self-adaptive sensor. It can be emphasised that this sensor will have a good application prospect in unattended long-term ocean observation system.

Ocean underwater vertical sensor structure is a kind of modern marine observation platform. But most of the current ocean sensors work independently, and it lacks a suitable method to assemble them in a control system. Having good expansibility and convenient structure, the ocean buoy platform with contactless data transmission technology is possible to organise a long-term, real-time and autonomous working observation network. The contactless data transmission model with a two-stage electromagnetic coupler is investigated. A prototype of communication system using the differential phase shift keying method is constructed. Due to attenuation in seawater, it is difficult to realise the long distance and low bit error rate transmission. To solve this problem, an equivalent two-terminal network model with compensation capacitor is proposed to make this contactless transmission system work at the resonance frequency. In 1000 m deep sea experiment, the sensors equipped with this vertical structure based on buoy platform show a perfect similarity of conductivity points like a commercial conductivity, temperature and depth device. It can be predicted that this underwater contactless data transmission method will be widely used to construct a multipoint distributed marine data network, and it can bring large scientific and economic values in deep sea exploration.

Fe-based amorphous alloys have advantages of low iron loss and high effective permeability, which are widely used in sensors and actuators. Power efficiency is one of the most important indicators among power conversion applications. We compared the magnetomechancial power conversion factors of metallic glassy ribbons FeCoSiB (Vitrovac 7600) and FeSiB (Metglas 2605SA1). We investigated the crystallization process under different annealing temperatures and tested the magnetomechancial coupling factors (k) and quality factors (Q) by using resonant and anti-resonant methods. We found that the maximum coupling factor of the annealed Vitrovac ribbons was 23% and the figure of merits k²Q was 4–7; however, the maximum coupling factor of the annealed Metglas ribbons was 73% and the maximum value of k²Q was 16. We can observe that the Metglas 2605SA1 ribbons have higher values of the magnetomechanical power efficiency than those of the Vitrovac 7600 ribbons, which means they are better to be used in subsequent research regarding acoustically driven antennas.