On the Linearity of Open Loop Fluxgate

An open loop ring-core fluxgate sensor is designed. Measured sensor parameters and building steps are presented. The sensor is built on a crystalline core stacked from circular permalloy laminations. All electronic parts are designed. A control card is manufactured and used in the experiment. Several measurements are performed to investigate the open loop linearity. Although the upper linear measurement limit for open loop fluxgate is accepted as 1 mu T in the literature, this study shows that open loop fluxgates can measure up to 15 mu T without any special circuitry. We propose the upper linear measurement limit of an open loop fluxgate to be defined as a function of demagnetization factor instead of the conventionally accepted 1 mu T value. This study shows that the measurement limit of an open loop fluxgate can be increased for a higher demagnetization factor at the expense of increased noise.