Capacitive sensor

• US 20050005703A1
• Filed: 06/23/2004
• Published: 01/13/2005
• Est. Priority Date: 07/11/2003
• Status: Abandoned Application

• Current Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Original Assignee: ALPS Electric Company Limited (Alps Alpine Co., Ltd.)
• Inventors: Saito, Junichi, Umeda, Yuichi
• Application Number:
  US10/875,251
• Publication Number:
  US 20050005703A1
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: A61B 5/1172 using fingerprinting
• CPC Class Codes: G01L 9/12 by making use of variations in capacitance , i.e. electric circuits therefor
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing

Abstract

A pressure-sensitive capacitive sensor includes a sensing unit in which a plurality of column wires and a plurality of row wires are formed in a matrix, a detecting signal generator, and filters. Capacitances at intersections between the column wires and the row wires change in accordance with externally applied pressure. The detecting signal generator sequentially outputs pulse signals of a predetermined frequency to the column wires of the sensing unit. The filters are connected to the respective row wires of the sensing unit and extract amplitudes of signals of the predetermined frequency. The amplitude is proportional to the capacitance at the intersection.

Claims

1. A pressure-sensitive capacitive sensor comprising:

a sensing unit comprising a plurality of column wires and a plurality of row wires in a matrix, capacitances at intersections between the column wires and the row wires changing in accordance with externally applied pressure, the sensing unit detecting changes in the capacitances at the intersections and a distribution of the externally applied pressure based on the detecting result of the changes;

a signal output unit for sequentially outputting pulse signals of a predetermined frequency to the column wires of the sensing unit; and

a plurality of filters connected to the respective row wires of the sensing unit and extracting signals of the predetermined frequency from signals received from the respective row wires.

5. The capacitive sensor according to claim 1, wherein the filter comprises a first capacitor disposed between an input terminal and the ground, an amplifier, a first resistor disposed between the input terminal and an output terminal of the amplifier, a second resistor disposed between the input terminal and an inverting input terminal of the amplifier, and a second capacitor disposed between the inverting input terminal and an output terminal of the amplifier.

6. The capacitive sensor according to claim 1, wherein a capacitor is connected in series to an input terminal of the filter.

2. A pressure-sensitive capacitive sensor comprising:

a sensing unit comprising a plurality of column wires and a plurality of row wires in a matrix, capacitances at intersections between the column wires and the row wires changing in accordance with externally applied pressure, the sensing unit detecting changes in the capacitances at the intersections and a distribution of the pressure based on the detecting result of the changes;

a signal output unit for sequentially outputting pulse signals of a predetermined frequency to the column wires of the sensing unit;

a selector for sequentially selecting and outputting signals received from the respective row wires of the sensing unit; and

a filter for extracting signals of the predetermined frequency from the signals output from the selector.

7. The capacitive sensor according to claim 2, wherein the filter comprises a first capacitor disposed between an input terminal and the ground, an amplifier, a first resistor disposed between the input terminal and an output terminal of the amplifier, a second resistor disposed between the input terminal and an inverting input terminal of the amplifier, and a second capacitor disposed between the inverting input terminal and an output terminal of the amplifier.

10. The capacitive sensor according to claim 2, wherein a capacitor is connected in series to an input terminal of the filter.

3. A capacitive sensor, comprising:

a sensing unit comprising a plurality of column wires and a plurality of row wires in a matrix, capacitances in the vicinity of intersections between the column wires and the row wires changing in accordance with irregularities on a surface of a measuring object distant from the sensing unit by a short distance, the sensing unit detecting changes in the capacitances in the vicinity of the intersections and the irregularities of the measuring object based on the detecting result of the changes;

a signal output unit for sequentially outputting pulse signals of a predetermined frequency to the column wires of the sensing unit; and

a plurality of filters connected to the respective row wires of the sensing unit and extracting signals of the predetermined frequency from signals received from the respective row wires.

8. The capacitive sensor according to claim 3, wherein the filter comprises a first capacitor disposed between an input terminal and the ground, an amplifier, a first resistor disposed between the input terminal and an output terminal of the amplifier, a second resistor disposed between the input terminal and an inverting input terminal of the amplifier, and a second capacitor disposed between the inverting input terminal and an output terminal of the amplifier.

11. The capacitive sensor according to claim 3, wherein a capacitor is connected in series to an input terminal of the filter.

4. A capacitive sensor, comprising:

a sensing unit comprising a plurality of column wires and a plurality of row wires in a matrix, capacitances in the vicinity of intersections between the column wires and the row wires changing in accordance with irregularities on a surface of a measuring object distant from the sensing unit by a short distance, the sensing unit detecting changes in the capacitances in the vicinity of the intersections and the irregularities of the measuring object based on the detecting result of the changes;

a signal output unit for sequentially outputting pulse signals of a predetermined frequency to the column wires of the sensing unit;

a selector for sequentially selecting and outputting signals received from the respective row wires of the sensing unit; and

a filter for extracting signals of the predetermined frequency from the signals output from the selector.

9. The capacitive sensor according to claim 4, wherein the filter comprises a first capacitor disposed between an input terminal and the ground, an amplifier, a first resistor disposed between the input terminal and an output terminal of the amplifier, a second resistor disposed between the input terminal and an inverting input terminal of the amplifier, and a second capacitor disposed between the inverting input terminal and an output terminal of the amplifier.

12. The capacitive sensor according to claim 4, wherein a capacitor is connected in series to an input terminal of the filter.