Circular Array of Magnetic Sensors for Current Measurement: Analysis for Error Caused by Position of Conductor

Abstract

This paper analyzes the measurement error, caused by the position of the current-carrying conductor, of circular array of magnetic sensors for current measurement. The circular array of magnetic sensors is an effective approach for AC or DC non-contact measurement, as its low cost, large linear range, wide bandwidth, light weight and low noise. Especially it has claimed that such structure has the excellent reduction ability for the errors caused by the position of the current-carrying conductor, crosstalk current interference, shape of the conduction cross section and the earth magnetic field. However, the positions of the current-carrying conductor, including un-center and un-perpendicularity, has not analyzed in detail until now. In this paper, the theoretical analysis has been proposed based on vector inner and exterior product. In the presented mathematical model of relative error, the un-center offset distance, the un-perpendicular angle, the radius of the circle and the number of the magnetic sensor are expressed in one equation. The comparison of the relative error caused by the position of the current-carrying conductor between four and eight sensors is conducted. The Tunnel Magnetoresistance (TMR) sensors are used in the experimental prototype to verify the mathematical model. The analysis results can be the reference to design the detail of circular array of magnetic sensors for current measurement in practical situation.

Contactless measurement of electric current using magnetic sensors

“…TMR sensors have also been used in current sensing [27] [28], but with accuracy that is limited by the non-linearity, hysteresis and poor offset stability of these devices ( Table 1).…”

“…The error caused by the position of the conductor in a circular array is analysed using AMR sensors in [85], using TMR sensors in [27], and using Hall sensors in [86]. When eight uncalibrated AMR sensors were used, the error caused by the current position was ±0.4%, and after calibration and correction the error decreased to ±0.06%.…”

A 3-phase current transducer based on microfluxgate sensors

“…To achieve this, 6 or 8 sensors are required for each phase [13] [14] [15][16][17]. Another advantage of these multisensor arrays is that they are immune to position changes of the measured conductor [18]. Sensors in the array may be divided into gradiometric pairs.…”