HIGH PRECISION FLUXGATE CURRENT SENSOR

Abstract

Nowadays the necessity to measure currents in the industrial worlds has been growth to the most important tools for proceedings controls. The classical approach of measuring current is by using a resistor and measuring the voltage drop across it. This method is fine for small currents however when the current levels increase to large values, it becomes more difficult. This is because the power dissipation in the resistor increases with the current squared. One solution for measuring large currents is by not directly measuring the current, but by measuring a property which is directly related to the current. By measuring the magnetic field around a conductor, the current level can be accurately predicted. Fluxgate current sensor uses a high permeability magnetic core to detect magnetic fields produced by a current flow through a conductor. Prodrive B.V. develops and uses a sensor with one fluxgate winding. However there is a disadvantage presented by this structure, that is the possibility of noise and ripple injection on the primary current measurement. In this final project, a second fluxgate winding was used to cancel the induced spurious signal on the sensing resistor. The targeted specifications of the new design are spurious signal up to 50μArms, noise performance up to 50nA/sqrt(Hz) and new operating switching frequency at 15kHz. Key Words: Fluxgate, Current Sensor, Second Fluxgate Winding, Spurious Peak, Noise.