Electricity: measuring and testing – Magnetic – Displacement
Reexamination Certificate
1998-03-06
2001-11-20
Patidar, Jay (Department: 2862)
Electricity: measuring and testing
Magnetic
Displacement
C324S207250
Reexamination Certificate
active
06320373
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a position sensor and a method for its operation, and more particularly, to a position sensor having several Hall elements which are selectively activated and deactivated.
BACKGROUND OF THE INVENTION
Position sensors in the form of angle encoders of the type having a magnetic graduation with a code structure have been known in the prior art. Applicant's German Patent Publication No. DE 44 42 371 A1 discloses distinguishing such graduations by a multi-track alternating magnetization of a dynamically balanced body which rotates proportionally in relation to the rotary movement supplied to the angle encoder. During rotation, this alternating magnetization is detected by static Hall elements which scan every track of the graduation and output an absolute position signal.
European Patent Publication No. EP 0 331 828 A1 discloses a multi-turn sensor which is basically composed of two measuring systems, an incremental optical measuring system and a magnetic detector. The incremental optical measuring system determines the exact position of an optical graduation during one revolution of the graduation and the magnetic detector determines the number of revolutions of the optical graduation. By using such a multi-turn sensor it is possible for a control unit to determine the absolute position of the optical graduation even after several revolutions of the optical graduation. When the multi-turn sensor is connected to a supply voltage, the stored number of revolutions and the stored incremental value are output so the absolute position is output immediately after power is supplied. To reduce the amount of electricity used by the multi-turn sensor, magneto-resistive elements having several hundred K&OHgr; of internal resistance are used and additional resistors are connected in series. In addition, digital component groups produced by CMOS technology are used.
A disadvantage of such a system is that the electrical power requirements of CMOS components increase with frequency so that at high processing speeds the requirement for electrical power is large. In addition, special magneto-resistive elements having a high internal resistance are required which makes further elaborate processing of their output signals necessary which introduces an increased sensitivity to noise in the system.
U.S. Pat. Nos. 4,780,703 and 4,796,005 disclose an incremental angle encoder where the position, or respectively the angle of rotation, is determined by an optical measuring system. The optical measuring system has a light source, a static graduation and a rotating graduation, as well as light-sensitive component groups with their associated electronic evaluation devices. To save energy, the light source and the electronic evaluation devices are connected with a supply voltage only long enough as is required to determine the position within the smallest graduation period. These component groups are otherwise disconnected from the energy supply.
A disadvantage with such a system is that because of the considerably higher current strengths required by the entire circuit arrangement while the light source and the electronic evaluation device are coupled to the supply voltage for only a short-time, interference often occurs.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to design a position sensor with a magnetic measuring system, and to disclose a method for its operation that considerably reduces the requirement for electrical power while minimizing the possibility of interference.
The method for operating a position sensor according to the present invention has an advantage that the Hall elements provided for the detection of a position are not all simultaneously switched on, interrogated and switched off, but instead are switched on, interrogated and switched off in a defined sequence. Since the maximum current requirement of the entire circuit arrangement is essentially determined by the current requirements of the Hall elements, it is possible to reduce the maximum current requirement considerably by the sequential activation and deactivation of the individual Hall elements.
Furthermore, only a small number of Hall elements are simultaneously switched on thus any interference that may be caused by the switching process is practically negligible. A time-delayed storage of the output signal of each Hall element is of further advantage because of which interference occurring in a stabilization phase of the Hall elements are suppressed. The position sensor according to the present invention has an advantage that it is possible to activate and deactivate individual Hall elements by individual control lines. In addition, each memory component group can be separately controlled by the control unit.
The position sensor and method for its operation according to the present invention will now be described by the drawings and explained in greater detail.
REFERENCES:
patent: 4728950 (1988-03-01), Hendrickson et al.
patent: 4780703 (1988-10-01), Ishida et al.
patent: 4796005 (1989-01-01), Ishida et al.
patent: 5258735 (1993-11-01), Allwine, Jr.
patent: 5313159 (1994-05-01), Allwine, Jr.
patent: 5528218 (1996-06-01), Rigsby
patent: 5530345 (1996-06-01), Murari et al.
patent: 5969495 (1999-10-01), Cherry, Jr. et al.
patent: 6088448 (2000-07-01), Poirel
patent: 44 42 371 A1 (1996-05-01), None
patent: 0 158 781 (1985-10-01), None
patent: 0 331 828 (1989-09-01), None
patent: 0 620 647 (1994-10-01), None
Brinks Hofer Gilson & Lione
Dr. Johannes Heidenhain GmbH
Patidar Jay
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