Induction-type position measuring apparatus

Abstract

An inductive linear encoder (,) has a position sensor (,) and scale (,) which are movably disposed relative to each other. The sensor (,) is with a drive wire (,) to which an alternating current is supplied, and one set of detection wires (,) at right angles to the drive wire (,) in the same plane. The scale (,) is configured including an elongate substrate (,) having its surface on which a series combination of conductive closed loop patterns (,) are periodically arranged at equal intervals. These conductive closed loop (,) are linearly laid out on the substrate (,) in the relative movement direction. Each loop (,) consists essentially of a reception conductor segment (,) and signal transmit conductor segments (,) integral with the former (,). The receive conductor segment (,) is responsible for generation of an induced current due to a first variable magnetic field creatable from the drive coil (,). The transmit conductor segments (,) are to create second variable magnetic fields that are opposite in polarity to each other and are perpendicular to the first magnetic field. Creation of such second magnetic fields results in flow of an induced current in the detector wire (,) of sensor (,), which in turn acts as a position detection output current.