METHODS AND SYSTEMS FOR SWITCHED CHARGE TRANSFER CAPACITANCE MEASURING USING SHARED COMPONENTS
First Claim
1. A system for measuring each of a plurality of measurable capacitances, the system comprising:
- a passive network, the passive network comprising at least one integrating capacitance and an isolating impedance statically coupled to the plurality of measurable capacitances, the at least one integrating capacitance configured to accumulate charge received from the plurality of measurable capacitances through the isolating impedance; and
a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each of the plurality of measurable capacitances by performing, for each selected measurable capacitance in the plurality of measurable capacitances, a charge transfer process for a number of times equal to at least two and a measuring process for a second number of times equal to at least one, wherein the charge transfer process comprises applying a pre-determined voltage to the selected measurable capacitance in the plurality of measurable capacitance with at least one of the plurality of digital outputs and then allowing the selected measurable capacitance to share charge with the passive network such that charge from multiple charge transfer processes accumulates on the at least one integrating capacitance of the passive network, and wherein the measuring process comprises quantizing a representation of a charge on the passive network to measure the selected measurable capacitance.
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Accused Products
Abstract
Methods, systems and devices are described for detecting a measurable capacitance using charge transfer techniques that can be implemented with many standard microcontrollers, and can share components to reduce device complexity and improve performance. In the various implementations of this embodiment, the passive network used to accumulate charge can be shared between multiple measurable capacitances. Likewise, in various implementations a voltage conditioning circuit configured to provide a variable reference voltage can be shared between multiple measurable capacitances. Finally, in various implementations a guarding electrode configured to guard the measurable capacitances can be shared between multiple measurable capacitances. In each of these cases, sharing components can reduce device complexity and improve performance.
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Citations
25 Claims
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1. A system for measuring each of a plurality of measurable capacitances, the system comprising:
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a passive network, the passive network comprising at least one integrating capacitance and an isolating impedance statically coupled to the plurality of measurable capacitances, the at least one integrating capacitance configured to accumulate charge received from the plurality of measurable capacitances through the isolating impedance; and a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each of the plurality of measurable capacitances by performing, for each selected measurable capacitance in the plurality of measurable capacitances, a charge transfer process for a number of times equal to at least two and a measuring process for a second number of times equal to at least one, wherein the charge transfer process comprises applying a pre-determined voltage to the selected measurable capacitance in the plurality of measurable capacitance with at least one of the plurality of digital outputs and then allowing the selected measurable capacitance to share charge with the passive network such that charge from multiple charge transfer processes accumulates on the at least one integrating capacitance of the passive network, and wherein the measuring process comprises quantizing a representation of a charge on the passive network to measure the selected measurable capacitance. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for measuring each of a plurality of measurable capacitances, the system comprising:
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at least one passive network, each passive network in the at least one passive network including at least one integrating capacitance and at least one isolating impedance, each of the at least one integrating capacitance and the at least one isolating impedance statically coupled to at least one of the plurality of measurable capacitances, the at least one integrating capacitance configured to accumulate charge received from the at least one of the plurality of measurable capacitances through the at least one isolating impedance; a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each of the plurality of measurable capacitances by performing, for each selected measurable capacitance in the plurality of measurable capacitances, a charge transfer process for a number of times equal to at least two and a measuring process for a second number of times equal to at least one, wherein the charge transfer process comprises applying a pre-determined voltage to the selected measurable capacitance in the plurality of measurable capacitances with at least one of the plurality of digital outputs and then allowing the selected measurable capacitance to share charge with the at least one passive network such that charge from multiple charge transfer processes accumulates on the at least one integrating capacitance of the at least one passive network; and
wherein the measuring process comprises quantizing relative to a threshold voltage a representation of a charge on the at least one passive network to measure the selected measurable capacitance.a voltage conditioning circuit coupled to the at least one passive network, the voltage conditioning circuit adapted to provide a variable reference voltage that varies with the threshold voltage. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15)
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16. A system for measuring each of a plurality of measurable capacitances, the system comprising:
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at least one passive network, each passive network in the at least one passive network including at least one integrating capacitance and at least one isolating impedance, each of the at least one integrating capacitance and the at least one isolating impedance statically coupled to at least one of the plurality of measurable capacitances, the at least one integrating capacitance configured to accumulate charge received from the at least one of the plurality of measurable capacitances through the at least one isolating impedance; a guarding electrode, the guarding electrode proximate each of the plurality of measurable capacitances; and a controller, the controller including a plurality of digital outputs, each of the plurality of digital outputs coupled to a measurable capacitance in the plurality of measurable capacitances, the controller configured to measure each selected measurable capacitance in the measurable capacitances by performing, for each of the measurable capacitances, a charge transfer process for a number of times equal to at least two and a measuring process for a second number of times equal to at least one, wherein the charge transfer process comprises applying a pre-determined voltage to the selected measurable capacitance in the plurality of measurable capacitances with at least one of the plurality of digital outputs and then allowing the selected measurable capacitance to share charge with the at least one passive network such that charge from multiple charge transfer processes accumulates on the at least one integrating capacitance of the at least one passive network; and
wherein the measuring process comprises quantizing a representation of a charge on the at least one integrating capacitance of the at least one passive network, the controller further configured to provide a guard signal to the guarding electrode using an output to guard the plurality of measurable capacitances during at least a portion of time in which the predetermined voltage is applied to the selected measurable capacitance and during at least a portion of the time in which the selected measurable capacitance shares charge with the at least one passive network. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25)
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Specification