The present invention relates in general to sensing devices for detecting magnetic fields, and more particularly to magnetic field sensing devices including multiple sensing elements such as hall effect based sensing elements.
A sensing device including a hall effect sensing element can be configured to detect the presence or absence of magnetic material. If used in conjunction with an appropriately place biasing magnet such a sensing element can be configured to detect the presence or absence of metals such as a tooth on a gear wheel. Sensors including such sensing elements are used to determine the position of CAMs and crankshafts in a modern gasoline or diesel internal combustion engine, or other mechanical linkages and rotating components.
In some applications, the positions are determined by switching (e.g., on or off) at a certain measurement point. For example, in some applications, the sensing element is configured to switch on or off depending on the strength of the detected magnetic field relative to a threshold value. In other applications, the sensor is configured to return an analogue signal indicative of mechanical position of the target object. For example, the sensor may provide a voltage signal proportional to the strength of a detected magnetic field.
The performance requirements of such systems can be demanding. The limits of accuracy and repeatability of the detection or measurement can be dominated by mechanical factors such as alignment, dimensional tolerances, assembly variation and wear.
Systems and methods for detecting the magnetic field created by a magnetic target are provided. A sensing device according to the invention includes an arrangement of multiple magnetic field sensing elements and circuit elements configured to select and/or interpolate between the sensing elements to give enhanced performance and to compensate for external mechanical factors. The circuit arrangement is integrated on a single silicon chip to form an integrated circuit sensing device in one embodiment.
According to the invention, a multiple sensing element arrangement is used together with control, selection and interpolation circuitry to improve the performance of Hall effect sensors and to allow for external mechanical tolerances and drifts to be determined and compensated. Digital memory is used to store measured and computed values for compensation.
According to an aspect of the present invention, a magnetic sensing device implemented on a single integrated circuit is provided. The device typically includes two or more magnetic sensing elements, wherein each sensing element is configured to produce an output signal based on the magnetic field detected by the sensing element, selection means for selecting the output signal of one or more of the sensing elements, and processing means for receiving the one or more selected output signals and for producing a sensing device output signal based on the one or more selected output signals. The device also typically includes control means for controlling the selection means to select the output signals of the sensing elements, and for controlling the processing means to execute an algorithm for processing of the selected output signals.
According to another aspect of the present invention, a magnetic sensing device is provided that typically includes a plurality of magnetic sensing elements, selection circuitry, control circuitry and processing circuitry implemented onto a single integrated circuit and configured such that an output of the sensing device is determined by the processing circuitry as a function of one or more of the outputs of the individual sensing elements.
According to yet another aspect of the present invention, an integrated magnetic sensing device implemented on a single silicon chip is provided. The device typically includes two or more magnetic sensing elements, wherein each sensing element is configured to produce an output signal based on the magnetic field detected by the sensing element, and a circuit arrangement configured to produce a sensing device output signal based on the output signals of one or more of the magnetic sensing elements.
Reference to the remaining portions of the specification, including the drawings and claims, will realize other features and advantages of the present invention. Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.