Device for contactless measuring of rotational angle or rotational speed

A device for contactless measuring at least one of rotational angle and a rotational speed of a shaft which is in one of stationary and rotational conditions, said device comprising a disk body fixedly and coaxially supported on said shaft for joint rotation therewith and having two opposing axial sides, at least one of said two axial opposing sides having a continuously extending concentric region formed of an electrically conductive material and comprising at least one uniformly widening segment, said disc body being formed of material which is different from the electrically conductive material said continuously extending concentric region is formed of;

• at least two sensor coils connected to an AC power source and arranged coaxially relative to each other on said two opposing sides, respectively, in a fixed position with respect to said disk body and operatively associated with said region of an electrically conductive material, each of said two sensor coils having an impedance which varies in accordance with a size of an area of said region of an electrically conductive material each of said two sensor coils are operatively associated with;
• and an evaluating circuit for measuring variations of the impedance of said two sensor coils to thereby measure the at least one of the rotational angle and the rotational speed by adding signals form said two sensor coils, all elements of said evaluating circuit being so selected that a substantially linear characteristic line is obtained for determining the at least one of the rotational angle and the rotational speed.