Abstract:
A system includes plural sensors to detect at least one of a magnetic field and an electrical field, where each of the plural sensors includes outputs that output sensor signals when a field is detected. Plural signal modulators receive sense signals that correspond to sensor signals from corresponding ones of the plural sensors. Each of the plural signal modulators has first and second control states. In the first control state, each signal modulator outputs sense signals, and, in the second control state, each signal modulator outputs inverted sense signals. A device receives and processes the sense signals or the inverted sense signals.

Description:
TECHNICAL FIELD 
   The invention relates to a sensor system with an arrangement of sensors in which each sensor detects an electric or magnetic field and outputs an electric sensor signal to its sensor outputs. The sensor outputs are connected to one another. In addition, the invention relates to a method to operate the sensor system. 
   BACKGROUND 
   A Hall sensor arrangement, in which several Hall sensors are arranged in a stationary manner and in a fixed configuration with one other, is known from the reference DE 199 43 128 A1. This type of sensor arrangement has the disadvantage that it has low flexibility in measuring magnetic fields, for example, because of a fixed connection of the sensors. In particular, the known sensor arrangement is not suitable for the two-dimensional and three-dimensional measurement of magnetic field distributions. 
   SUMMARY 
   As a result, the objective of the present invention is disclosing a sensor system that has a plurality of applications and that is suitable for analyzing two-dimensional and three-dimensional magnetic field distributions. 
   A sensor system is disclosed that has an arrangement of sensors. Each of the sensors detects an electric or magnetic field and outputs an electric sensor signal to its outputs. The same types of sensors but also different types of sensors can be used for the sensor system. 
   Each of the sensors is connected to a signal modulator, wherein the inputs of the signal modulator are connected to the sensor outputs of the related sensor. Each signal modulator has at least two control states. In a first control state, the corresponding basic sensor signal is fed to the signal modulator output as a sensor end signal. In a second control state, the inverted basic sensor signal is fed to the signal modulator output as a sensor end signal. 
   In addition, the sensor system features a device for the addition of the sensor end signals to a system signal. 
   The advantage of the sensor system is that a plurality of configurations can be defined for the sensor system because of the different control states of each signal modulator. As a result, the sensor system can be used flexibly and, in particular, to analyze two-dimensional and three-dimensional magnetic fields. In addition, such a sensor system is suitable for detecting linear, magnetic or electrical fields, and for detecting locational displacements of linear or axial, sinusoidally-distributed magnetic fields. 
   In addition, a method to operate the sensor system that is made possible for the first time with the sensor system in accordance with the invention is disclosed. In this arrangement, all control states of the signal modulators together define the configuration of the sensor system. The operating method features the following steps: 
   In a first step, the sensor system is put into a first configuration. A suitable device detects and stores the system signal output by the sensor system. 
   In a second step of the operating method, the sensor system&#39;s configuration is modified from the first configuration to the second configuration. In this arrangement, the second configuration differs from the first configuration. 
   In a third step, the system signal output by the sensor system in the second configuration is in turn read in and stored in a suitable device. 
   If necessary, yet other configurations can be set and the signals output by the sensor system can be read in and stored. 
   Finally, in a further method step, an arithmetic operation is performed with the first and second and any additional system signals. This arithmetic operation can be used to draw conclusions about the two-dimensional or spatial distribution of the magnetic or electrical field being detected. 
   Hall sensors, for example, can be used as the sensors in the sensor system. These types of Hall sensors can be designed as vertical or lateral Hall sensors on the basis of silicon sensors. But magnetic-field-dependent resistors can also be considered as sensors. 
   An operational transconductance amplifier can amplify the basic sensor signals output by the Hall sensors. This operational transconductance amplifier is then connected between each sensor and the corresponding signal modulator. The use of operational transconductance amplifiers to amplify the basic sensor signals makes it possible to connect, in parallel, individual sensor units comprised of a sensor and the associated signal modulator. This type of parallel connection makes it possible to add up currents of the sensor end signals to a system signal. 
   The signal modulators can be connected with a control logic circuit, which allows the switchover between two control states of a signal modulator to be realized via digital control words. This allows particularly quick switching between two control states of a signal modulator and therefore between two configurations of the sensor system. 
   In an exemplary embodiment of the sensor system, the sensors can be arranged in a plane. Within such a plane, the sensors can in turn be arranged in rows and columns, which are orthogonal to one another. As a result, a checkerboard-like grid of sensors is realized. 

   
     DESCRIPTION OF THE DRAWINGS 
     The invention is described in greater detail in the following on the basis of exemplary embodiments and the associated figures. 
       FIG. 1  shows a component of a sensor system in a schematic circuitry arrangement. 
       FIG. 2  shows an example of a sensor system in accordance with the invention in a schematic circuitry arrangement. 
       FIG. 3A  shows a first configuration of a sensor system in accordance with the invention. 
       FIG. 3B  shows another configuration of the sensor system from  FIG. 3A . 
       FIG. 4A  shows a cylindrical permanent magnet whose orientation is determined relative to the sensor system from  FIGS. 3A and 3B . 
       FIG. 4B  shows the tangential magnetic field amplitude on the X-axis of the magnet from  FIG. 4A  along centric circles with the radius X about the axis of symmetry. 
       FIG. 4C  shows a top view of the relative position of a sensor system in accordance with  FIG. 3A  to a magnet in accordance with  FIG. 4A . 
       FIG. 4D  shows the tangential magnetic field amplitude. 
   

   DETAILED DESCRIPTION 
     FIG. 1  shows a Hall sensor  10  whose outputs  21 ,  22  are connected to an operational transconductance amplifier  70 . The outputs of the operational transconductance amplifier  70  are in turn connected to the inputs  41 ,  42  of a signal modulator  30 . The sensor end signal iop, ion is fed to the outputs  51 ,  52  of the signal modulator  30 . The output modulator  30  is connected to a control logic circuit  8 , which can create the various control states in the signal modulator  30 . To do this, digital signals are fed to the inputs EN, P, M of the control logic circuit  8  and these digital signals can be summarized as digital control words. In this arrangement, the input EN of the control logic circuit  8  stands for turning on the signal modulator  30 . As soon as the signal “high” is fed to the input EN of the control logic circuit  8 , the signal modulator  30  supplies a signal to its outputs  51 ,  52  that is a function of the signal from the Hall sensor  10 . If the signal “low” is fed to the input EN of the control logic circuit  8 , the signal modulator  30  is deactivated, i.e., the outputs  51 ,  52  of the signal modulator  30  are not connected to the sensor outputs  21 ,  22  of the Hall sensor  10 . When the signal modulator  30  is activated, there is the possibility of receiving either the basic sensor signal of the Hall sensor  10  or the inverted basic signal of the Hall sensor  10  at the outputs  51 ,  52  of the signal modulators  30  via feeding corresponding signals to the inputs P, M of the control logic circuit  8 . To do this, the signal “high” must be fed just to input P or the signal “high” to input M. 
   Overall, the signal modulator  30  in  FIG. 1  has three different control states. These control states are characterized by 0 (signal modulator  30  deactivated),+(addition, i.e., the sensor end signal iop, ion corresponds to the basic sensor signal) and−(i.e., the sensor end signal represents the inverted basic sensor signal). 
     FIG. 2  shows the connection of two sensors  10  from  FIG. 1  to a sensor system. Each sensor  10 ,  11  is allocated to a signal modulator  30 ,  31 , which is connected to the corresponding sensor  10 ,  11  via an operational transconductance amplifier  70 ,  71 . The sensor outputs  21 ,  22  of the sensor  10  or the sensor outputs  23 ,  24  of the sensor  11  are connected to the sensor inputs  41 ,  42  of the signal modulator  30  or the inputs  43 ,  44  of the signal modulator  31 . Sensor end signals are fed to the outputs  51 ,  52  or  53 ,  54  of the signal modulators  30 ,  31  and these signals are summed up for addition via the device  6 . 
   According to  FIG. 2 , the device  6  for addition is a simple parallel circuit of the output voltages being fed to the outputs  51 ,  52  or  53 ,  54  of the signal modulators  30  or  31 . With respect to the currents measured in this case, an addition of the sensor end signals is produced. The summed currents generate a voltage drop at the resistors  91 ,  92 , which can be read out as the system signal VOP, VON. 
   The signal modulators  30 ,  31  each contain a control logic circuit, which is not shown in  FIG. 2 , however. Only the inputs of the control logic circuits with EN 0 , P 0 , M 0  for the signal modulator  30  or EN 1 , P 1 , M 1  for signal modulator  31  are indicated. 
     FIG. 3  shows the arrangement of four sensors  10 ,  11 ,  12 ,  13  in a square pattern, wherein the surface is divided into quadrants Q 0 , Q 1 , Q 2 , Q 3 . One of the sensors  10 ,  11 ,  12 ,  13  is located in each quadrant Q 0 , Q 1 , Q 2 , Q 3 . The configuration of the sensor system from  FIG. 3A  is indicated by the + symbol in quadrants Q 0 , Q 3  and by the − symbol in quadrants Q 2 , Q 1 . According to  FIG. 3B , the sensor system from  FIG. 3A  has a different configuration, wherein the + symbol applies to quadrants Q 1  and Q 0  and by the − symbol to quadrants Q 2  and Q 3 . The + or − symbols indicate the control state of the sensor  10 ,  11 ,  12 ,  13  located in the respective quadrant Q 0 , Q 1 , Q 2 , Q 3 . Using a sensor system in two different configurations K 1  and K 2  according to  FIGS. 3A and 3B , the rotational angle of a magnet according to  FIG. 4A , for example, can be measured via the sensor arrangement. 
     FIG. 4A  shows a cylindrical permanent magnet whose orientation is determined relative to the sensor system from  FIGS. 3A and 3B . 
   Such a magnet  9  is depicted in  FIG. 4A . It has the shape of a disk, which possesses an axis of symmetry along the Z-axis. Both halves of the disk are diametrically magnetized and consequently feature a magnetic north pole N and a magnetic south pole S. 
     FIG. 4B  shows the tangential component of the magnetic field with respect to circles about the axis of symmetry Z as magnetic field amplitude B, wherein the magnetic field is applied at the intersection point of a circle with the X-axis. For a circle with radius X 1 , the tangential component of the magnetic field has magnetic field amplitude B 0 . 
     FIG. 4C  shows a top view of the arrangement of a magnet  9  in accordance with  FIG. 4A  over a sensor system according to  FIG. 3A . The sensors  10 ,  11 ,  12 ,  13  lie on a circle around the axis of symmetry Z of the magnet  9 , wherein the radius of the circle is X 1 . The axis of symmetry Z of the magnet  9 , the sensor  10  and the Y-axis of the magnetic  9  enclose angle α 1 . The angle α 1  is 45°. 
     FIG. 4D  shows, as a function of angle a from  FIG. 4C , the tangential magnetic field amplitude B along the circle with the radius x 1  according to  FIG. 4C . The position of the sensors  10 ,  11 ,  12 ,  13  is indicated in  FIG. 4D . The maximum value of the magnetic field amplitude is produced for a α=90°. In this case, the magnetic field amplitude has the value B 0 . The magnet  9  can now be rotated according to  FIG. 4C , in the direction of the arrow, vis-à-vis the sensor arrangement. If one designates the rotational angle of the magnet  9  vis-à-vis the sensors system as α, then when 
   G Hall =the electric amplification of the Hall sensors the following relations are produced: 
   The magnetic source field B source  at the location of each sensor  10 ,  11 ,  12 ,  13  is determined by the rotational angle α in accordance with:
 
 B   source   =B   0 ·sine(α).
 
   In the configuration according to  FIG. 3A , the following is obtained as the system signal V K1 :
 
 V   K1   =B   0 · G   Hall ·((sine(α+45)−sine(α+135)−sine(α+225)+sine(α+315)))
 
   The following is yielded by transformation:
 
 V   K1 =2√{square root over (2)} ·B   0   G   Hall ·sine(α).
 
   Another signal is obtained with the configuration of the sensor system according to FIG.  3 B:
 
 V   K2   =B   0 · G   Hall ·((sine(α+45)−sine(α+135)−sine(α+225)+sine(α+315)))
 
   Transformation yields:
 
 V   K2 =2√{square root over (2)} ·B   0 · G   Hall ·cosine(α).
 
   The rotational angle of magnet  9  vis-àvis the sensor system can be computed in a simple manner from signals V k1  and V k2  using an arithmetic operation. To do so, the following is calculated:
 
α=ARC TAN( V   K2   :V   K2 )
 
   This calculation can be performed, for example, using the method in accordance with the invention by the sensor system measuring at a first point in time in a configuration K 1  and the measured value of the system signal (VOP, VON) being stored. Then, as seen in  FIGS. 3A and 3B , the sensor system is put into another configuration K 2 . Then the system signal VOP, VON is again recorded and stored. Finally, the arithmetic operation indicated above is performed. 
   Because of the possibility of controlling the signal modulators via digital control words, the switchover between different configurations K 1 , K 2  of the sensor system can take place in a very short time, for example at intervals of several μs. As a result, this guarantees that the sensor system has a high level of flexibility and great speed.