Inductive displacement measuring device for motor car, has measurement circuit determining reference value for magnetic permeability of plunger based on inductance of calibration coil, and measuring coil enclosed by casing

摘要

The device has a ferromagnetic measuring plunger (18) movable back and forth into a cylindrical measuring coil (12). A measurement circuit measures inductance of the coil depending on displacement of the plunger. A calibration measuring coil (20) is arranged on the plunger and displaced axial to the measuring coil and coaxial to the measuring coil. The measurement circuit determines a reference value for magnetic permeability of the plunger based on the inductance of the calibration coil. The measuring coil is closely enclosed by a ferromagnetic casing (40). The casing is made of high magnetic permeability material. The measuring coil is designed as an air coil and a cylindrical bucking coil (14).