Low Magnitude Direct Current Sensor Characteristics Improvement

Abstract

The paper describes fluxgate leakage current sensor characteristics improvement techniques, which can be useful to obtain optimal bandwidth and sensitivity. For direct current leakage current sensor, the sensitivity and bandwidth are the most important because high sensitivity allows for higher insulation resistance measurement and working with lower line voltages while a high bandwidth provides for the safe line disconnection time on failure. In fluxgate current sensors design, there is a tradeoff between bandwidth and sensitivity, which makes it difficult to produce a DC line protection device with high sensitivity and bandwidth. At the same time in the area of space magnetometers, there are significant achievements in the magnetometers' characteristics improvement, including sensitivity and bandwidth. Fluxgate current sensors have a similar structure and operating principles with fluxgate magnetometers, therefore some of the techniques can be adopted. In this paper, the authors discuss fluxgate current sensor characteristics improvement methods and suggest a sensor schematic with enhanced bandwidth and response time. The developed circuit model of fluxgate current sensor simplifies early steps of sensor development providing a sufficient estimate of sensor oscillation frequency and gain. To confirm modeling results, a prototype of the proposed sensor was developed.