Diagnosis of electrical failures in capacitive sensors

A capacitive sensor, comprising:

• a first conductive structure;
• a second conductive structure that is counter to the first conductive structure, wherein the second conductive structure is movable relative to the first conductive structure in response to an external force acting thereon, wherein the second conductive structure is capacitively coupled to the first conductive structure to form a first capacitor having a first capacitance that changes with a change in a distance between the first conductive structure and second conductive structure, wherein the first capacitance is representative of the external force and the first capacitor comprises a first micro-electromechanical (MEMS) output configured to output a first sense signal representative of the first capacitance;
• a second capacitor comprising a first terminal and a second terminal, the first terminal being coupled to the first MEMS output of the first capacitor in order to receive the first sense signal and the second terminal being configured to output a second sense signal based on the first sense signal;
• an amplifier comprising a first amplifier input coupled to the second terminal of the second capacitor and configured to output a first amplified signal and a second amplified signal based on the second sense signal, wherein the first amplified signal is in phase with the second sense signal and the second amplified signal is 180° out of phase with the second sense signal;
• and
• a diagnostic circuit configured to receive a first pair of signals including the first amplified signal and the second amplified signal, generate a first offset measurement based on the first pair of signals, wherein the first offset measurement is representative of a degree of pattern similarity between the first amplified signal and the second amplified signal, compare the first offset measurement to a first threshold range defined by a first threshold and a second threshold, and detect a first fault on a condition that the first offset measurement is outside of the first threshold range,
• wherein the diagnostic circuit comprises:
• a comparator circuit configured to compare the first offset measurement to the first threshold range and activate a first fault signal on the condition that the first offset measurement is outside of the first threshold range;
• and
• an error processing circuit configured to receive the first fault signal and generate a second fault signal in response to the first fault signal being activated, uninterrupted, for a predetermined time interval, wherein the second fault signal is indicative of a confirmation of the first fault.

A capacitive sensor, comprising:

• a first conductive structure;
• a second conductive structure that is counter to the first conductive structure, wherein the second conductive structure is movable relative to the first conductive structure in response to an external force acting thereon, wherein the second conductive structure is capacitively coupled to the first conductive structure to form a first capacitor having a first capacitance that changes with a change in a distance between the first conductive structure and second conductive structure, wherein the first capacitance is representative of the external force and the first capacitor comprises a first micro-electromechanical system (MEMS) output configured to output a first sense signal representative of the first capacitance;
• an amplifier comprising a first amplifier input coupled to the first MEMS output for receiving the first sense signal and configured to output a first amplified signal and a second amplified signal based on the first sense signal, wherein the first amplified signal is in phase with the first sense signal and the second amplified signal is 180° out of phase with the first sense signal;
• and
• a diagnostic circuit configured to:
• receive a first pair of signals including the first sense signal and the first amplified signal, generate a first offset measurement based on the first pair of signals, wherein the first offset measurement is representative of a degree of pattern similarity between the first sense signal and the first amplified signal, compare the first offset measurement to a first threshold range defined by a first threshold and a second threshold, and detect a first fault on a condition that the first offset measurement is outside of the first threshold range, or
• receive a second pair of signals including the first sense signal and the second amplified signal, generate a second offset measurement based on the second pair of signals, wherein the second offset measurement is representative of a degree of pattern similarity between the first sense signal and the second amplified signal, compare the second offset measurement to a second threshold range defined by a third threshold and a fourth threshold, and detect a second fault on a condition that the second offset measurement is outside of the second threshold range,
• wherein the diagnostic circuit comprises:
• a comparator circuit configured to compare the first offset measurement to the first threshold range and activate a first fault signal on the condition that the first offset measurement is outside of the first threshold range;
• and
• an error processing circuit configured to receive the first fault signal and generate a second fault signal in response to the first fault signal being activated, uninterrupted, for a predetermined time interval, wherein the second fault signal is indicative of a confirmation of the first fault.

A capacitive sensor, comprising:

• a first conductive structure;
• a second conductive structure that is counter to the first conductive structure, wherein the second conductive structure is movable relative to the first conductive structure in response to an external force acting thereon, wherein the second conductive structure is capacitively coupled to the first conductive structure to form a first capacitor having a first capacitance that changes with a change in a distance between the first conductive structure and second conductive structure, wherein the first capacitance is representative of the external force and the first capacitor comprises a first micro-electromechanical system (MEMS) output configured to output a first sense signal representative of the first capacitance;
• a third conductive structure that is counter to the first conductive structure, wherein the third conductive structure is movable relative to the first conductive structure, wherein the third conductive structure is capacitively coupled to the first conductive structure to form a second capacitor having a second capacitance that changes with a change in a distance between the first conductive structure and third conductive structure, wherein the second capacitance is representative of the external force and the second capacitor comprises a second MEMS output configured to output a second sense signal representative of the second capacitance;
• an amplifier comprising a first amplifier input coupled to the first MEMS output for receiving the first sense signal and configured to output a first amplified signal based on the first sense signal and comprising a second amplifier input coupled to the second MEMS output and configured to output a second amplified signal based on the second sense signal;
• and
• a diagnostic circuit configured to receive a first pair of signals including the first sense signal and the first amplified signal, generate a first offset measurement based on the first pair of signals, wherein the first offset measurement is representative of a degree of pattern similarity between the first sense signal and the first amplified signal, compare the first offset measurement to a first threshold range defined by a first threshold and a second threshold, and detect a first fault on a condition that the first offset measurement is outside of the first threshold range,
• wherein the diagnostic circuit comprises:
• a comparator circuit configured to compare the first offset measurement to the first threshold range and activate a first fault signal on the condition that the first offset measurement is outside of the first threshold range;
• and
• an error processing circuit configured to receive the first fault signal and generate a second fault signal in response to the first fault signal being activated, uninterrupted, for a predetermined time interval, wherein the second fault signal is indicative of a confirmation of the first fault.