Capacitive displacement sensor
First Claim
1. A capacitive distance measuring system, comprising:
- at least one capacitive sensor configured as differential capacitor, which includes at least two transmitting electrodes and one or more counter electrodes, arranged opposite and at a distance to the respective transmitting electrodes, such that they can be displaced relative to the transmitting electrodes and that at least two partial capacitors are formed, wherein the capacitance of at least one partial capacitor changes in proportion to the distance, a trigger unit adapted to feed binary trigger signals with rising and descending edges at predetermined moments to selected transmitting electrodes that form partial capacitors of the differential capacitor for generating measuring signals, wherein the trigger signals for the two partial capacitors have a fixedly determined phase offset relative to each other, a processing device that evaluates the measuring signals for determining the partial capacitances of the differential capacitor and from the distance to be measured and that selects specific edges of the triggering signals to be used for generating measuring signals to be evaluated, and a switch unit for defining time windows in which the selected edges of the trigger signals are positioned, so that the associated measuring signals can pass through and be evaluated in the processing unit.
1 Assignment
0 Petitions
Accused Products
Abstract
A distance measuring system (1) is provided with a capacitive sensor (7a, 7b), designed in the form of a differential capacitor (18), for which the partial capacitors (C1, C2 have capacitances that depend on the position to be determined. The system also includes a processing device (5) for determining the desired distance that contains, for example, a sigma/delta demodulator. The partial capacitors (C1, C2) are triggered periodically with binary signals, wherein the trigger signals from the one partial capacitor (C1) are transmitted with a phase offset to the signals from the other partial capacitor (C2). The processing device (5) determines which trigger signals must be used for the evaluation. Within time windows that are synchronized with the edges of the trigger signals, a switch unit (22) allows the associated receiving signals to pass through to the processing unit (5) and blanks out all other signals. The distance measuring system (1) makes it possible to have a low number of interpolation errors with high resolution and long interpolation periods. The distance measuring system (1) can be expanded by adding two essentially independent, parallel-operating relative measuring systems to form an absolute distance measuring system, which determines the absolute position solely from the current measuring values. A nearly optional enlargement of the measuring range is possible by adding further relative measuring systems.
42 Citations
38 Claims
-
1. A capacitive distance measuring system, comprising:
-
at least one capacitive sensor configured as differential capacitor, which includes at least two transmitting electrodes and one or more counter electrodes, arranged opposite and at a distance to the respective transmitting electrodes, such that they can be displaced relative to the transmitting electrodes and that at least two partial capacitors are formed, wherein the capacitance of at least one partial capacitor changes in proportion to the distance, a trigger unit adapted to feed binary trigger signals with rising and descending edges at predetermined moments to selected transmitting electrodes that form partial capacitors of the differential capacitor for generating measuring signals, wherein the trigger signals for the two partial capacitors have a fixedly determined phase offset relative to each other, a processing device that evaluates the measuring signals for determining the partial capacitances of the differential capacitor and from the distance to be measured and that selects specific edges of the triggering signals to be used for generating measuring signals to be evaluated, and a switch unit for defining time windows in which the selected edges of the trigger signals are positioned, so that the associated measuring signals can pass through and be evaluated in the processing unit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
-
-
30. A distance measuring system, comprising:
-
at least two capacitive sensor configured as differential capacitors, which include transmitting electrode rows each having a constant partition that differs for the rows, and an associated counter electrode rows, arranged opposite and at a distance to the respective transmitting electrodes, such that they can be displaced relative to the transmitting electrodes and that at least two partial capacitors are formed, wherein the capacitance of at least one partial capacitor changes in proportion to the distance, a trigger unit adapted to feed binary trigger signals with rising and descending edges at predetermined moments to selected transmitting electrodes that form partial capacitors of the differential capacitor for generating measuring signals, wherein the trigger signals for the two partial capacitors have a fixedly determined phase offset relative to each other, a processing device that evaluates the measuring signals for determining the partial capacitances of the differential capacitor and from this the distance to be measured and that selects specific edges of the triggering signals to be used for generating measuring signals to be evaluated, and a switch unit for defining time windows in which the selected edges of the trigger signals are positioned, so that the associated measuring signals can pass through and be evaluated in the processing unit. - View Dependent Claims (31, 32, 33, 34, 35, 36, 37, 38)
-
Specification