Capacitive Sensor Signal Conditioning Multiplexing
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Solution Overview
Problem
Existing sensor systems for occupant supports face challenges in efficiently calibrating and diagnosing multiple capacitive sensors, particularly in vehicle seats, which complicates the measurement of physiological data and requires complex signal conditioning stages, increasing costs and board space.
Innovation Solution
A system comprising capacitive sensors, a multiplexer, a programmable gain amplifier (PGA), an oscillator, and a controller that selects and diagnoses sensors using channel and diagnostic select signals, allowing for simultaneous voltage and frequency readings to determine sensor status and adjust gain, thereby simplifying diagnostics and calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple signal conditioning stages are used for each capacitive sensor, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges multiple signal conditioning stages into a single shared stage that serves multiple capacitive sensors. The programmable gain amplifier (PGA) and oscillator are configured to handle signals from different sensors sequentially, eliminating the need for separate conditioning circuits for each sensor while maintaining measurement precision through software-controlled gain adjustment and frequency modulation.
Solution Approach 2:
The signal conditioning circuitry is designed with universal functionality to handle multiple sensor types and configurations. The PGA can be programmed with different gain values for different sensors, and the oscillator can be tuned to different frequencies, allowing a single circuit to perform the work of multiple dedicated circuits while reducing overall system complexity.
2Measurement precision
If multiple signal conditioning stages are used for each capacitive sensor, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple signal conditioning stages into a single shared stage that serves multiple capacitive sensors. The programmable gain amplifier (PGA) and oscillator are configured to handle signals from different sensors sequentially, eliminating the need for separate conditioning circuits for each sensor while maintaining measurement precision through software-controlled gain adjustment and frequency modulation.
Solution Approach 2:
The signal conditioning circuitry is designed with universal functionality to handle multiple sensor types and configurations. The PGA can be programmed with different gain values for different sensors, and the oscillator can be tuned to different frequencies, allowing a single circuit to perform the work of multiple dedicated circuits while reducing overall system complexity.
3Measurement precision
If multiple signal conditioning stages are used for each capacitive sensor, then measurement precision is improved, but board space increases
Solution Approach 1:
The patent merges multiple signal conditioning stages into a single shared stage that serves multiple capacitive sensors. The programmable gain amplifier (PGA) and oscillator are configured to handle signals from different sensors sequentially, eliminating the need for separate conditioning circuits for each sensor while maintaining measurement precision through software-controlled gain adjustment and frequency modulation.
Solution Approach 2:
The patent transitions from a spatial arrangement where each sensor has its own dedicated signal conditioning circuit (2D plane occupation) to a temporal arrangement where a single shared circuit services multiple sensors through time-multiplexed operation. This dimensional shift from space to time allows precise measurement of multiple sensors without proportionally increasing board space.
4Measurement precision
If complex calibration procedures are implemented for multiple sensors, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The system implements self-service calibration where the controller automatically performs calibration procedures for multiple sensors without requiring manual intervention. The controller sequentially configures the PGA and oscillator for each sensor, executes calibration routines, and stores calibration data automatically, eliminating the need for operators to manually calibrate each sensor while maintaining high precision.
Solution Approach 2:
The calibration process incorporates feedback mechanisms where the controller monitors sensor responses and automatically adjusts calibration parameters to achieve optimal precision. The system uses the oscillator frequency responses and PGA output signals to verify calibration accuracy and make real-time adjustments, ensuring precise measurements without complex manual procedures.
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 system reduces system complexity and costs by eliminating multiple signal conditioning stages, providing efficient diagnostics for multiple sensors and reducing board space requirements while accurately measuring physiological data.
Implementation Method 1
The oscillator includes an input and an output. A frequency of the output depends on a capacitance coupled to the input.
Data Source
AI summary
A system includes multiple capacitive sensors, a multiplexer, a programmable gain amplifier, an oscillator, a switch, and a controller. The sensors are coupled to the multiplexer, the multiplexer is coupled to the switch, and the switch is coupled to the amplifier and the oscillator. The controller may control the multiplexer to select each of the sensors. The controller may control the switch to activate the amplifier or the oscillator. The controller may measure voltage output by the amplifier or frequency output by the oscillator. The system may be included in an occupant support such as a vehicle seat.