This work presents an approach to monitoring the State-Of-Charge of Lithium-Ion battery cells via piezo disc-based ultrasonic Time-Of-Flight measurement by measuring the traveling time of a mechanical pulse through the cell between two surface-mounted sensors. The main advantage of this approach is the simplicity and the resulting low cost, which makes it suitable for future application in battery management systems. In detail, the excitation of the piezo actuator is done using a single semiconductor switch instead of a power amplifier, and the received signal is processed with an amplifier and Schmitttrigger combination to condition the signal for the microprocessor, which is part of a battery management system. Both the functionality and the limits of the design are evaluated with a high energy density Lithium-Ion pouch cell under different operational scenarios. Several parameters such as temperature, current rates, and excitation frequency are varied to prove the design concept. For validation purposes, an estimation function is generated and a real-world driving cycle applied. An estimation with an error of 1.29% of the Time-Of-Flight total value or 16.8%of the State-Of-Charge value under challenging conditions is achieved with the current setup.

Preserving the stable operation and proper functionality of the electric power grid is of utmost importance. Integral grid components such as power transformers are negatively affected by occurring disturbances. In particular, the time course and distribution on the different phases of direct currents within the transmission grid, among them geomagnetically induced currents, is of great interest. In this paper, we report on the development of a fiber optic current sensor exploiting the Faraday effect intended to observe these direct currents on all three phases of a high-voltage power grid. The proposed low-cost sensor is constructed with an adjustable phase retarder and a single-mode sensing fiber. A linear current relationship for direct currents down to 1A was observed. From the sensor signal, the presence of a direct current bias superimposed on an alternating current can be identified. Simulations based on a Jones formalism model provided application limits of the single-mode sensing fiber. Furthermore, we developed a calibration procedure to counteract temperature-induced variations of the sensor scale factor within the fiber-optic coil and achieve a maximum current error of 0.5% down to a rated current of 5A in a range from 15-65°C.

Temperature is a crucial factor for the safe operation of lithium-ion batteries. During operation, the internal temperature rises above the external temperature due to poor inner thermal conductivity. Various sensors have been proposed to detect the internal temperature, including fiber Bragg grating sensors. However, to the authors’ knowledge, there is no detailed description of the encapsulation of the fiber Bragg grating sensor in the literature to shield it from strain. In this study, different encapsulation methods for strain compensation were compared to find the encapsulation material most compatible with the electrolyte. For this, we stored the proposed sensors with different encapsulation methods in ethylene carbonate:ethyl methyl carbonate (EC:EMC) 3:7 with LiPF₆ (lithium hexafluorophosphate) electrolyte and applied temperature changes. After evaluating the sensor encapsulation methods in terms of handling, diameter, uncertainty, usability, and hysteresis behavior, the most suitable sensor encapsulation was found to be a fused silica capillary with polyimide coating.

This paper presents a novel wayside rail monitoring system for real-time detection and quantification of rail surface cracks with sub-millimeter precision. The core innovation lies in mounting piezoelectric transducers on the web of the rail—an unconventional and practical location that avoids interference with wheel passages while enabling continuous monitoring in real-world conditions. Moreover, to directly quantify crack depth, a customized signal processing pipeline is developed, employing surface acoustic waves (SAWs) and incorporating a parallel reference transducer pair mounted on an undamaged rail section for calibration. This auxiliary pair provides a real-time calibration baseline, improving measurement robustness and accuracy. The method is experimentally validated on rail samples and verified through metallographic analysis. This approach enables condition-based maintenance by improving detection accuracy and offers the potential to reduce operational costs and enhance railway safety.

To estimate the mass emissions of combustion sources, the accurate determination of the exhaust mass flow with reasonable time resolution is a key requirement. State of the art flowmeters are often based on the measurement of the time of flight of ultrasonic bursts. Such systems are not well suited for harsh environment due to the fact that they expose their sensitive Piezo-transceiver directly to the measured medium. To tackle these challenges, we are presenting a new principle for an ultrasonic flow sensor.