A new simple and sensitive dilatometer to measure magnetostriction of ribbons has been developed,based on an optical fiber sensor using an annular photodiode. The optical fiber is used bidirectionally, both for emission and detection of light, simplifying the access to the ribbon under test. The working principle is based on the measurement by reflection of the longitudinal displacement of the ribbon end. For a Vitroperm amorphous ribbon of 100 mm length, 21 (mu)m thickness, and 8.3 mm width, a displacement of 2.571 (mu)m with a maximum uncertainty of 8 nm has been obtained.
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