Measurement System for Accurate Determination of Fast-Changing DC Currents up to 900 A

• Published in: IEEE transactions on instrumentation and measurement Vol. 72; p. 1
• Main Authors: Zeng, Keqiu, Rietveld, Gert, Popovic, Jelena, Yu, Hui
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.01.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: 30 Measurement technique; Correlation analysis; Current measurement; Current measurements; DC current; Direct current; High resolution; Magnetic resonance imaging; Measurement methods; Noise analysis; Noise measurement; Noise reduction; Power amplifiers; Power measurement; Pulse measurements; Reproducibility; Reproducibility of results; Resistors; Voltage measurement; Zero-flux
• ISSN: 0018-9456; 1557-9662
• DOI: 10.1109/TIM.2023.3277995

Accurate measurement of fast-changing direct current (DC) is of great importance for high-power, high-resolution amplifiers generating fast-changing pulsed DC currents, as for example used in magnetic resonance imaging systems. A setup and a comprehensive measurement method is developed for the accurate determination of fast-changing DC currents up to 900 A for evaluating these amplifiers. By using a comprehensive analysis method, the predominant factors and noise sources affecting the accurate determination of the amplifier current pulse reproducibility are studied. To further reduce the noise of the readout electronics in the measurement system, a noise reduction method based on correlation analysis is developed. Experiments have subsequently been carried out to prove the validity of the theorical analysis and the design method. The experiments show that a single measurement channel achieves a current pulse reproducibility of around 1.1 μAs. Using two channels and the correlation analysis method gives around 80 % improvement in the measurement noise, resulting in a current pulse reproducibility of around 0.25 μAs, which is more than a factor 20 improvement with respect to the state of the art. These results and the successful final application of the new setup in an actual high-power, high-resolution power amplifier confirm the effectiveness of this new measurement method.