High Resolution Inductive Position Sensor
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
State-of-the-art thin-film magnetic heads (1 in Fig. 1) with open coils are used as inductance sensors in a collinear set-up on a ceramic block (2 in Fig. 1) to detect the relative position of a periodic metal grid structure (3 in Figs. 1 and 2) in the submicron range. Fig. 1 is a cross-sectional view of the grid structure in the direction of movement of ceramic block 2. A circuit (Fig. 3), comprising, say, three inductance sensors, utilizes an interpolation concept known per se, by means of which the grid period is divided into subportions by comparing the inductance of each coil with the average value of the various coils. The three sensor coils 4 of the magnetic heads are wired to form three identical resonators 5. Resonators 5 are used to feed the output of an oscillator circuit 6 to a set of differential amplifiers 7.