Signal-balanced shield electrode configuration for use in capacitive displacement sensing systems and methods

Abstract

A capacitive encoder includes a signal-balanced shield electrode configuration that does not require electrical ground connection or active sensing and control in order to maintain the shield electrode(s) at a sufficiently constant voltage during capacitive position measurements. The shield electrode configuration is positioned in a capacitive coupling gap between transmitter electrodes and receiver electrodes during operation. The shield electrode configuration is patterned in a manner that complements the layout of the transmitter electrodes, such that the shield electrode configuration inherently floats at a nominally constant electrical potential when coupled to the signals present on the transmitter electrodes. The resulting capacitive encoder is thus more economical to build, convenient to install, and reliable during operation than capacitive encoders which use an electrical connection, compensation drive circuitry, or grounding in order to control the potential of a shield member that operates at a potential that is not inherently constant.

Description

FIELD OF THE INVENTION [0001] This invention relates generally to displacement sensing capacitive encoders, and more particularly to capacitive encoders including a scale having signal-balanced shield electrode configuration that does not require an electrical connection or grounding of the shield electrode, in order to provide low cost, reliable, and high accuracy displacement sensing. BACKGROUND OF THE INVENTION [0002] Numerous capacitance-type measuring devices for making linear and angular displacement or position measurements have been developed wherein two members that are fixed relative to each other include respective capacitive electrodes that are capacitively coupled between the two support members and a third member is relatively movable between the two members to alter their capacitive coupling. The third member alters their capacitive coupling in a manner corresponding to the position of the third member relative to the first two members. The capacitive coupling affects...

AI Technical Summary

Benefits of technology

[0025] Hence, the invention overcomes the disadvantages of prior art capacitive displacement sensing devices that use electrically connected, externally coupled, or ac...

Problems solved by technology

It should be appreciated that the electrical connections and or capacitive coupling provided by the embodiments indicated above may be inconvenient, unreliable, or “insufficient” to effectively and fully ground the shield electrode in a variety of desirable capacitance-type measuring device configurations and applications.

Furthermore, the amplifier circuitry indicated above that feeds back a cap...

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