- Patent Title: Capacitive displacement sensing circuit with a guard voltage source
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Application No.: US14839228Application Date: 2015-08-28
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Publication No.: US09826308B2Publication Date: 2017-11-21
- Inventor: Roderick B. Hogan , Scott P. Porter , Ruchir M. Dave
- Applicant: Apple Inc.
- Applicant Address: US CA Cupertino
- Assignee: APPLE INC.
- Current Assignee: APPLE INC.
- Current Assignee Address: US CA Cupertino
- Agency: Blakely, Sokoloff, Taylor & Zafman LLP
- Main IPC: H04R3/00
- IPC: H04R3/00 ; H04R9/06

Abstract:
A common plate is formed in a moveable element of a device, the device having an actuator coupled to drive the moveable element. A first plate and the common plate together form a first capacitance, while a second plate and the common plate together form a second capacitance, both of which varies as a function of displacement of the moveable element. A measurement circuit has an input coupled to the first plate, while an excitation voltage source has an output coupled to the second plate. A guard voltage source has an output coupled to a conductive portion of the device. Other embodiments are also described and claimed.
Public/Granted literature
- US20160241957A1 Capacitive Displacement Sensing Circuit With A Guard Voltage Source Public/Granted day:2016-08-18
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