Magnetic field sensor for stable magnetic field measurement over a wide temperature range

US6150811A · kind A · utility

Assignee

• Mannesmann VDO AG · DE

Inventors

• Thomas Grill · Villingen-Schwenningen, DE
• Helmut Bacic · Rehna, DE
• Martin Gruler · Aixheim, DE
• Oliver Springmann · Dresden, DE

Key dates

• Filing date: Apr 18, 1998
• Grant date: Nov 21, 2000
• Expiry date: Apr 18, 2018

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R33/02
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

A magnetic field sensor consists of a cylinder (2) with a core of premagnetized amorphous ferromagnetic metal. The inductance of the coil (2) is controlled by earth magnetic field H.sub.E and forms part of an L.C. oscillator (1). An adjusting device is provided to smooth out fluctuations from a target value in the oscillator frequency caused by the action of the field H.sub.E on the oscillator coil (2). This is done by allowing another adjustable magnetic field to influence the inductance (2) of the oscillator (1): the adjustable magnetic field is generated by a second coil (3) in the form of a compensating coil and the current flux (1) through the second coil (3) is controlled by the adjusting device in such a way that the magnetic field generated by the second coil (3) compensates for the action of the field H.sub.E on the first coil (2); and a control logic element (8) changes the polarity of the current flux (I) through the compensating coil (3) at a rate which matches the fluctuations with time of the field H.sub.E by synchronous actuation of switches (9a) and (9b). Where the field H.sub.E is present for both current directions, the respective compensating currents are measure…