Giant magnetoresistive based galvanically isolated voltage measurement

Nowadays direct current (DC) is much more widely used than a decade ago. Not only in the well-known high voltage direct current (HVDC) transmission but also as DC powered marine system, DC data center and DC fast charging system for electric vehicles. DC is now challenging the alternative current (AC) in a large variety of fast growing markets. However a galvanically isolated DC voltage measurement for low and medium voltage is, from the technical and scientific point of view, still far behind the AC voltage measurement methods. In this paper a new giant magnetoresistive (GMR) based sensor system for galvanic isolated DC voltage measurement is introduced. The measurement system consists mainly of a special coil arrangement with low inductance, a GMR sensor, AD converters and a low-cost FPGA. The voltage sensor system showed an outstanding measurement accuracy of 0.3% for voltage values up to ±550V in a temperature range from -30°C to 90°C. This completely new approach for the galvanic isolated measurement of electric voltages avoids the use of bulky magnetic components and expensive power consuming analog electronics.