Development of a proximity contactless ammeter based on GMR sensors for measuring direct currents

Conventional ammeters are inserted in series with the element in which the current is to be measured, constituting an invasive measurement form. Clamp ammeters measure non-invasively but are limited to alternating currents. For continuous currents measurements, Hall-based clamp ammeters are used, with low output voltages and little stability to temperature. Also, the need to involve the conductor in a magnetic core makes it impractical for some situations. This manuscript describes a proximity contactless ammeter based on giant magnetoresistance sensors capable of measuring direct currents some centimeters away from the conductor, non-invasively and with high resolution. Sixty tests were performed, with currents varying from −3 A to 3 A, with steps of 0.1 A. The prototype was able to estimate the current with type A expanded uncertainties of 100 mA and 0.19 cm for the distance. The results demonstrate the feasibility of conducting contactless current measurements using GMR sensors.