CAPACITIVE FORCE SENSOR

• US 20080250864A1
• Filed: 04/10/2008
• Published: 10/16/2008
• Est. Priority Date: 04/11/2007
• Status: Active Grant

• Current Assignee: Silverbrook Research Pty Limited
• Original Assignee: Silverbrook Research Pty Limited
• Inventors: Shipton, Gary
• Granted Patent: US 7,891,253 B2
• Time in Patent Office: Days
• US Class Current: 73/780
• CPC Class Codes: G01D 2205/90 Two-dimensional encoders, i.e. having one or two codes extending in two directions
• CPC Class Codes: G01D 5/3473 Circular or rotary encoders
• CPC Class Codes: G01D 5/34746 Linear encoders
• CPC Class Codes: G01L 1/144 with associated circuitry G01L1/146 and G01L1/148 take precedence
• CPC Class Codes: G01L 1/146 for measuring force distributions, e.g. using force arrays G01L1/148 takes precedence
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

A force sensor is provided which has a capacitive sensor circuit incorporating a sensor capacitor having variable capacitance C_sen arranged so that an output of the capacitive sensor circuit is proportional to 1/C_sen.

Claims

1. A force sensor comprising a capacitive sensor circuit incorporating a sensor capacitor having variable capacitance C_sen arranged so that an output of the capacitive sensor circuit is proportional to 1/C_sen.

2. A force sensor as claimed in claim 1, wherein the sensor capacitor is a parallel plate capacitor having one fixed plate and one movable plate.

3. A force sensor as claimed in claim 2, wherein the movable plate is configured to move relative to the fixed plate due to a pressure force exerted on the movable plate thereby altering separation of the plates and said capacitance C_sen.

4. A force sensor as claimed in claim 2, wherein a compression spring is connected to the movable plate.

5. A force sensor as claimed in claim 1, wherein the sensor capacitor is positioned within a capacitive feedback circuit of the capacitive sensor circuit such that one of the plates of the sensor capacitor is connected directly to the capacitive sensor circuit.

6. A force sensor as claimed in claim 5, wherein the capacitive sensor circuit is a sigma-delta convertor circuit.