Bridge-based impedance sensor system
AssigneeAnalog Devices, Inc.
InventorsIsaac Chase Novet, Steven J. Decker
Life of this patent
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Abstract
An impedance sensing circuit includes three impedance elements and a sensing element arranged in a bridge configuration. A first input terminal is coupled to two of the impedance elements to apply a stimulus signal. In a mutual-sensing mode, a second input terminal is coupled to the third impedance element and the sensing impedance element to apply an opposite phase stimulus signal. The impedance sensing circuit may be configured in a self-sensing mode, in which the opposite phase stimulus signal is decoupled from the third impedance element and the sensing impedance element. At least one of the impedance elements is variable and may be adjusted to balance an offset impedance load on the sensing element.
Claims20
A sensing circuit comprising:
- an input terminal;
- a first impedance element coupled between the input terminal and a first output terminal, the first impedance element is a variable impedance element;
- a second impedance element coupled between the input terminal and a second output terminal;
- a third impedance element coupled to the second output terminal;
- a coupling network coupled to the first output terminal;
- and
- an amplifier circuit coupled to the first output terminal and the second output terminal, the amplifier circuit to output a voltage related to an environmental characteristic sensed by a sensing impedance element coupled to the coupling network.
A sensor system comprising:
- a driver circuit to generate a periodic stimulus signal;
- an impedance bridge comprising a first impedance element, a second impedance element, and a third impedance element, wherein the first impedance element is a variable impedance element;
- an input terminal coupled to the driver circuit and coupled to the impedance bridge to apply the stimulus signal to the impedance bridge;
- a coupling network coupled to a first output terminal of the impedance bridge;
- and
- an amplifier circuit coupled to the first output terminal and a second output terminal of the impedance bridge, the amplifier circuit configured to output a voltage based on signals from the first output terminal and the second output terminal.
Dependencies are inferred from the claim text.