CROSS-REFERENCE TO RELATED APPLICATION

This application is a non-provisional of U.S. application Ser. No. 62/775,931 filed Dec. 6, 2018, and U.S. application Ser. No. 62/942,826 filed Dec. 3, 2019, which are both herein incorporated by reference.

FIELD OF TECHNOLOGY

The present application relates to a capacitive proximity sensor, in particular, capacitive sensors for proximity sensing and discrimination.

BACKGROUND

Existing capacitive sensors have no or limited ability to distinguish between different types of objects or substances.

For these and other reasons, there is a need for the present invention.

SUMMARY

According to an embodiment of a capacitive sensing system for detecting an object, the capacitive sensing system includes a capacitive sensing pad, a conductive discriminating pad, a switch, a capacitance measurement circuit and a controller. The conductive discriminating pad is in proximity to the capacitive sensing pad. The switch includes an input terminal coupled to the discriminating pad. The switch selectively couples the discriminating pad to a voltage potential of the capacitive sensing pad or to a ground potential. The capacitance measurement circuit detects a capacitance value of the capacitive sensing pad. The controller is operable to measure the capacitance value of the capacitive sensing pad when the discriminating pad is coupled to the capacitive sensing pad voltage potential or to the ground potential. The capacitive measurements taken provide data about the properties of the object. This data can be used to identify, and/or distinguish between, different objects, materials or liquids.

According to a method of identifying an object or substance, the method includes providing a capacitive sensing pad and n conductive discriminating pads where n≥1, providing a shield driver that provides a voltage potential of the capacitive sensing pad, and providing n switches that each have an input terminal coupled to one of the n discriminating pads and have two switch connection states which selectively couple the input terminal to the capacitive sensing pad voltage potential or to the ground potential, wherein the n switches are operable to provide 2nunique connection states for the n discriminating pads. The method includes placing the object in proximity to the capacitive sensing pad. The method includes measuring up to 2ncapacitance values of the capacitive sensing pad that each correspond to one of the 2nunique connection states for the n discriminating pads. The method includes determining a capacitance value for the object or substance by comparing a first set of the 2ncapacitance values and a second set of the 2ncapacitance values. The method includes identifying the object or substance by comparing the capacitance value to one or more reference capacitance values for reference objects or substances having the same and/or different material properties as the object or sub stance.

According to an embodiment of a method of identifying an object or substance, the method includes providing a capacitive sensing pad and n conductive discriminating pads where n≥1, providing a shield driver that provides a voltage potential of the capacitive sensing pad, and providing n switches that each have an input terminal coupled to one of the n discriminating pads and have two switch connection states which selectively couple the input terminal to the capacitive sensing pad voltage potential or to the ground potential, where the n switches are operable to provide 2nunique connection states for the n discriminating pads. The method includes placing the object or substance in proximity to the capacitive sensing pad. The method includes taking capacitive measurement sets of the object or substance, where each measurement set corresponds to 2ncapacitance values measured using the capacitive sensing pad for the 2nunique connection states for the n discriminating pads. The method includes determining a mathematical relationship between the capacitive measurement sets and known dielectric constants or dipole moments of the object or substance. The method includes identifying the object or substance based on the mathematical relationship and the known dielectric constants or dipole moments of the object or substance.

Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings.

