The Development of Fluxgate Magnetometer for Non–Destructive Measurement

Abstract

Pengukuran tanpa musnah bahan feromagnet dan gangguan medan magnet frekuensi rendah memerlukan penderia medan magnet yang mempunyai kepekaan yang tinggi dan stabil. Magnetometer yang berasaskan prinsip fluxgate dan memenuhi ciri-ciri yang diperlukan telah dibina dengan menggunakan teras gelang ferit. Teras gelang ferit ini dipacukan dengan sumber arus untuk mencapai keadan histerisis. Gelung pengesan yang dililit merentasi gelang ferit akan mengesan perubahan medan magnet yang berlaku pada gelang ferit tersebut. Teknik pengesanan yang digunakan adalah berasaskan pengesanan harmonik kedua oleh suatu pengesan fasa. Penderia fluxgate yang dibina adalah murah mudah dibina, mampu mengesan arah medan magnet dan tahan lasak. Kata kunci: Fluxgate; penderia medan magnet; histerisis; feromagnet Non–Destructive measurements of ferromagnetic material and low frequency magnetic flux distrubance require a highly sensitive and stable magnetic sensor with directional capabilities. A magnetometer based on fluxgate principle that meets the requirement had been developed using a ferrite ring core. The ferrite ring core is excited by an excitation current source to achieve hysteresis condition. The pick up coil that is wound across the ring core will pick up the magnetic flux generated in the ring core. This sensing method is based on the conventional type of fluxgate magnetometer with detection of second harmonics by a phase sensitive detector. Major advantages of the fluxgate magnetometer are low cost, directional, easy to construct, reliable and rugged. Key words: Fluxgate; magnetic sensor; hysteresis; ferromagnetic