Koninklijke Philips Corporation N.v.

U.S. Philips Corporation

Nxp B.v.

Michael Muth

August Petersen

Volker Graeger

Adrian Harmansa

To provide a circuit arrangement for controlling a sensor by means of a power supply source which is connected to input terminals of the sensor, and an evaluation circuit which is connected to output terminals of the sensor, by means of which the current consumption of a sensor in the standby state can be reduced in a simple manner, the power supply source () is switchable between at least two current levels in dependence upon an output signal level (S) of the sensor ().

Circuit arrangement for controlling a sensor

A method for offset compensation of a magnetoresistive position or angular position measuring system includes at least one Wheatstone bridge with four locally offset magnetoresistive resistors to which a DC voltage is applied and past which a permanent magnet is moved, wherein the respective bridge voltage is measured, by which method a subsequent offset compensation of magnetoresistive position or angular position measuring systems is also possible on site. Provision is made for a calibration cycle to be run through upon start-up of the measuring system, by moving the permanent magnet past the bridge(s) for a measuring cycle, evaluating the extreme values of the bridge voltages measured during this procedure by deriving the mean values thereof, and deriving from these mean values corresponding compensation values in the form of offset values to be taken into consideration by the measuring system, the compensation values being stored in a register.

Method for offset compensation of a magnetoresistive position or angular position measuring system

Circuit arrangement

In an evaluation circuit for evaluating an output signal of a magnetoresistive sensor ( ) for rotational speed measurement, in which the evaluation circuit performs an offset compensation of the sensor signal and comprises a comparator ( ) which receives the offset compensated sensor signal and compares it with a reference voltage, a reliable identification of the output signal of the sensor after switching on the arrangement is ensured in that, in an initial mode, the value of the reference voltage is selected in dependence upon the temperature, the temperature dependence being approximated to that of the sensor signal, in that a control unit ( ) is provided which, in the initial mode, consecutively checks whether the sensor signal is present, triggers the offset compensation only after the presence of said signal, subsequently checks whether the comparator ( ) supplies an output signal, and changes over to a control mode only after the presence of said signal, in which control mode the temperature dependence of the reference voltage is switched off and, instead, the reference voltage is adjusted to approximately 40% of the maximum amplitude of the offset-compensated sensor signal.

Evaluation circuit for a magnetoresistive sensor

An angle sensor includes at least two angularly spaced sensor units which measure in a contactless manner and whose sensor voltages are similar but angularly shifted sinusoidal functions (sensor characteristic) of the angle .alpha. to be measured relative to a rotatable element and a processing circuit forms an angle sensor voltage which is a measure of the angle .alpha.. Using limited analog circuitry, a wide angular range is obtained and also a monotonously increasing angle sensor voltage which is dependent as linearly as possible on the angle to be measured, in that the sensor voltages are direct voltages which are constant in time. The processing circuit includes limiter circuits (15) whose input receives the sensor voltages (UMA, UMB), and whose output voltages exhibit values (10, 11) which remain constant when a limit value of the sensor voltages is exceeded, and that the output voltages of the limiter circuits (15) are applied to the input of a summing circuit (16) in order to form the angle sensor voltage.

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Stelle, Germany

Michael Muth