H. Nakesch et H. Pfutzner, MAGNETOSTRICTIVE AMORPHOUS SENSOR FOR THE DETECTION OF HUMAN RESPIRATION, Journal of magnetism and magnetic materials, 133(1-3), 1994, pp. 634-636
A simple sensor for the detection of respiratory and cardiac activity
is based on changes in the circumference of the human thorax. The sens
or consists of magnetostrictive amorphous ribbons glued to the convex
side of a prebent nonmagnetic layer. As a result, elongation is transf
erred into compressive stress, which reduces the ribbon's permeability
, and a proportional voltage signal, respectively. The paper discusses
major practical problems which result from the material's nonlinear b
ehaviour, the sensor's individual transfer function, its undefined pre
-stress and the elasticity of the applied sensor belt. In an effective
way, overall linearization can be attained by means of wide-range cal
ibration functions stored in a computer file. Alternatively, scaling b
y means of a spirometer yields quantitative evaluations, but restricte
d to respiration.