Position measuring instrument

US5386642A · kind A · utility

Assignee

• DR. JOHANNES HEIDENHAIN GMBH · DE

Inventors

• Alfons Spies · Munich, DE
• Gerald Metz · St. Georgen, DE

Key dates

• Filing date: Feb 4, 1993
• Grant date: Feb 7, 1995
• Expiry date: Feb 4, 2013

Classification

• Technology area (CPC G): Physics
• CPC primary: G01P13/04
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A position measuring instrument for measuring the relative position of two objects movable relative to one another. The position measuring instrument comprises a periodic measurement scale division having a period t and a scanner unit, wherein the scanner unit and the periodic measurement scale division move relative to one another in a measuring direction. In addition, the scanner unit comprises four groups (A-D) each comprising at least four magnetoresistive elements (A.sub.n -D.sub.n) (n=1, 2, 3, 4, . . .), which are interconnected in the form of a series-parallel circuit to form a half bridge circuit having an upper branch and a lower branch. The upper branch comprises a magnetoresistive element from each group (A-D) and the lower branch comprises a corresponding magnetoresistive element from each group (A-D). Furthermore, the magnetoresistive elements of the upper branch are offset from the corresponding magnetoresistive elements of the lower branch by t/2. The position measurement instrument further comprises an evaluation device to form position measurement values from position-dependent output signals generated by the magnetoresistive elements in response to relative moveme…