Field and force sensors using amorphous ribbons

Amorphous ribbon is sensitive to magnetic field and has a large tensile strength. By making use of these distinctive features, excellent sensors can be constituted. This paper presents two types of sensors: a magnetic field and a tensile force sensors. On the magnetic sensor, zero flux method is introduced for detection of field level in a ribbon magnetized with external field to be detected. High sensitivity and accuracy is achieved. These performances are not affected with demagnetization effects, sizes and shapes of the ribbon utilized. Applying this technique to dc leak current sensing, the order of 0.0002% of main dc current which flows into a pair of one-turn conductors can be detected. On the tension sensor, the lowest order frequency mode of transverse vibrations in a ribbon is available. The frequency is proportional to a square root of the force. When the ribbon is excited with magnetic force of the same frequency, any position on the ribbon oscillates in-phase with the exciting force. Using this in-phase relation, an adaptive sensing is performed like a PLL (phase locked loop).