Capacitive Sensor Noise Detection Circuit
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Solution Overview
Problem
Conventional capacitive sensors face issues with noise interference, leading to misdetection in capacitance measurement, particularly in vehicle seating and grip detection applications, due to complex circuit configurations required for noise detection across various frequency bands.
Innovation Solution
A capacitive sensor design incorporating a sensor circuit, noise detection circuit, and control circuit that alternately measures capacitance and noise using impedance elements, allowing for sensitive noise measurement across specific frequency bands with a simple configuration, and switches between measuring capacitance and noise based on threshold detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a subcarrier signal is transmitted and demodulated to detect noise, then noise detection capability is improved, but device complexity increases due to modulation and demodulation circuits
Solution Approach 1:
The patent extracts the noise detection function from the capacitance measurement function by using a separate noise detection circuit that measures noise through an impedance element independently of the main sensor circuit. This allows noise to be detected without requiring complex modulation and demodulation circuits, thereby reducing device complexity while maintaining noise detection capability.
Solution Approach 2:
The patent introduces an impedance element as an intermediary component that couples the sensor electrode to both the sensor circuit and the noise detection circuit. This intermediary allows the noise detection circuit to measure noise with high sensitivity according to the frequency characteristic of the impedance element without directly complicating the main measurement path.
2Measurement precision
If multiple frequency bands are monitored for noise, then measurement precision is improved, but device complexity increases due to multiple detection circuits
Solution Approach 1:
The patent makes the single noise detection circuit multi-functional by coupling it to the sensor electrode through an impedance element that provides frequency-selective coupling. The same noise detection circuit can measure noise across multiple frequency bands (including the drive frequency and harmonics) by utilizing the frequency characteristic of the impedance element, eliminating the need for separate detection circuits for each frequency band.
Solution Approach 2:
The patent changes the operating parameters of the noise detection circuit by adjusting the frequency characteristic of the impedance element. By modifying the impedance element's parameters (such as its inductance or capacitance values), the system can selectively measure noise at different frequencies using the same hardware circuit, thereby achieving multi-frequency monitoring without increasing circuit count.
3Productivity
If capacitance and noise are measured simultaneously, then productivity is improved, but measurement precision deteriorates due to mutual interference
Solution Approach 1:
The patent implements periodic action by alternately switching between capacitance measurement and noise measurement modes. The control circuit sequentially activates the sensor circuit for capacitance measurement and the noise detection circuit for noise measurement, rather than attempting to operate both simultaneously. This time-division approach eliminates mutual interference while maintaining high measurement productivity through rapid alternating measurements.
Solution Approach 2:
The patent segments the measurement function into two separate, dedicated circuits: a sensor circuit for capacitance measurement and a noise detection circuit for noise measurement. Each circuit is optimized for its specific function and operates independently at different times. This segmentation allows both measurement functions to be performed with high precision without mutual interference, while the control circuit coordinates their operation to maintain high productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively reduces misdetection by measuring noise with high sensitivity across different frequency bands, improving the accuracy of capacitance and grip detection without increasing circuit complexity.
Implementation Method 1
the noise can be measured with the sensitivity according to the frequency characteristic of the first impedance element
Implementation Method 2
the sensor circuit measures capacitance of the sensor electrode
Data Source
AI summary
Capacitive sensor includes sensor electrode, sensor circuit that is electrically connected to sensor electrode measures capacitance of sensor electrode, first impedance element, noise detection circuit that is electrically connected to sensor electrode through first impedance element and measures noise, and control circuit that switches between on and off of each of sensor circuit and noise detection circuit. Control circuit causes sensor circuit to measure the capacitance of sensor electrode by turning on sensor circuit and by turning off noise detection circuit and control circuit causes noise detection circuit to measure the noise by turning off sensor circuit and by turning on noise detection circuit.