Lust Antriebstechnik Gmbh

Brose Fahrzeugteile Gmbh & Co Kg, Coburg

Imo Institut Fur Mikrostrukturtechnologie Und Optoelektronik E.v.

Institut Fuer Mikrostrukturtechnologie Und Optoelektronik E.v.

Lust Electronic-systeme Gmbh

Sensitec Gmbh

Fritz Dettmann

Uwe Loreit

Hilmar Dohles

Karl-Heinz Lust

Gunter Schepp

J&uuml;rgen Kunze

Torsten Schönbach

Jurgen Kunze

Carsten Möller

Heike Bischoff

Wolfgang Fritz

The invention relates to a system for pulse magnetizing high-precision magnetic scales. The system comprises a shaped current conductor () and a pulse current source () that is composed of a capacitor bank (), a transfer switch () and a control unit (). The compact set-up of the system is the prerequisite for a power circuit that has such a low resistance that the required high pulse currents are obtained at supply voltages of below 60 V. The transfer switch is an H bridge with four switches () that contain equal numbers of MOS transistors connected in parallel. The short pulse times that are achieved using the MOS transistors allow the use of shaped current conductors with which magnetized areas can be produced with a very high precision. The inventive system provides a means for saving components, electric power and time by a factor of up to 100.

System for writing magnetic scales

In at least one measuring rod of the length measurement system the direction of magnetization lies in the plane of its cross-section which is perpendicular to the direction of measurement and forms a magnetization pattern. In the simplest case the magnetization of the cross-section is homogeneous. As one advances in the direction of measurement the magnetization pattern is increasingly rotated in relation to the starting end of the measuring rod. This magnetization results in a magnetic field whose direction is also continuously rotated as one advances in the direction of measurement. By means of at least one magnetic field sensor which responds to the direction of the magnetic field the prevailing field angle for each position is determined and can be clearly assigned to the position for a multitude of different variants of the length measurement system.

Length measurement system with at least one magnetic measuring rod

The invention relates to a method for evaluating signals while eliminating an interference signal on magnetoresistive sensor elements which is preferably proportional to the zero offset. The sensor elements can form a sensor element array such as a sensor bridge. According to the invention, the direction of magnetization of the sensor elements is modulated or shifted by applying a magnetic pulse field of a modulated or variable direction, and the output signals of the sensor elements or of the sensor element array are fed to a differential amplifier. Due to the modulation or shift of the operating voltage of the sensor bridge, the modulation or shift resulting at the same time as the magnetization of the sensor elements, a signal often arises which includes a direct component that is proportional to the magnetic field to be measured, and has an alternating component that is proportional to the offset voltage of the sensor element array. The latter is minimized by a feedback or is adjusted to zero. The bandwidth, with which the direct voltage that is proportional to the magnetic field to be measured can follow changes of the input signal, is greater in magnitude than the magnetization frequency of the sensor elements.

Method for evaluating signals of magnetoresistive sensors with high band width

A sensor assembly for measuring current I.sub.o is disclosed. The sensor assembly includes four magnetoresistive resistors (1, 2, 3, 4) arranged to form a Wheatstone bridge. The bridge is disposed over a U shaped conductor 14. The resistors are arranged so that two resistors (1,2) forming one bridge branch are disposed over one leg of the conductor and the two resistors (3,4) forming the other bridge branch are disposed over the other leg of the conductor. Each resistor is formed out of a number of magnetoresistive strips (1', 2', 3', 4'). The magnetoresistive strips forming the individual bridge branch resistors are interleaved so as to ensure the resistors forming each bridge branch have substantially the same temperature. When current I.sub.o is applied to the conductor, the equal and opposite magnetic fields that develop around the individual bridge branches cause the Wheatstone bridge to produce a signal U.sub.a that is a function of the current.

Sensor assembly

To measure magnetic field gradients is difficult because sensor elements available for this have only a limited linearity range due to their sensitivity which is strongly dependent on the temperature and on auxiliary-field magnetic fields and furthermore this sensitivity has a significant sample dispersion. Whereas now the arrangement of a a Wheatstone bridge with magnetoresistive resistors is such that on the one hand two symmetrical areas are provided, in each area of which a resistor of a bridge branch is arranged, and that moveover all other building elements are also designed with a high degree of symmetry. With this a symmetrical temperature gradient is created in the sensor chip, which gradient does not influence the output signal of the bridge. A temperature-dependent zero-point drift does also not exist. The changeable resistor needed for trimming is as the single singular structural part directly arranged on the central axis and also does not interfere with the measurement. The arrangement is particularly suited for the potential-free measurement of the current intensities.

Sensor assembly for measuring current as a function of magnetic field

Magnetic field sensor constructed from a remagnetization line and one

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Wetzlar, Germany

Fritz Dettmann