Particulate Matter Sensor Capacitance Measurement Without Switches
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Solution Overview
Problem
Existing particulate matter (PM) detection systems in diesel automobiles require expensive switches to separate bias voltage application and measurement, leading to increased sensor costs due to high OFF-state resistance needs.
Innovation Solution
A sensor structure that measures capacitance change without using a switch by applying bias voltage and forming a magnetic field to induce PM resistance, using a power supply unit and measurement unit separated electrically, with Mega ohm resistance for minimal capacitance output and maximum capacitance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a switch is used to separate bias voltage application and measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the switching function from the sensor structure by separating the power supply unit that applies bias voltage from the measurement unit that measures capacitance. This allows the measurement to be performed without requiring a switch within the sensor itself, thereby reducing device complexity while maintaining measurement precision through electrical separation of the two functions.
Solution Approach 2:
The patent introduces an intermediary measurement unit that measures capacitance changes caused by PM-induced resistance changes. This intermediary measurement approach allows indirect detection of PM levels without requiring direct switching operations, thus simplifying the overall sensor structure while preserving measurement accuracy.
2Measurement precision
If a switch with high OFF-state resistance is used, then measurement precision is improved, but sensor cost increases
Solution Approach 1:
The patent removes the expensive high OFF-state resistance switch from the sensor structure by extracting the voltage application function into a separate power supply unit. This eliminates the need for costly specialized switches while maintaining the ability to perform accurate capacitance measurements through the separated measurement unit.
Solution Approach 2:
The patent replaces expensive reusable components (high OFF-state resistance switches) with simpler, more cost-effective circuit implementations using standard resistors and capacitors. The measurement system achieves its function through passive components rather than expensive active switching devices, reducing overall sensor cost.
3Reliability
If bias voltage is applied continuously, then PM induction is improved, but energy consumption increases
Solution Approach 1:
The patent implements periodic application of bias voltage through the separated power supply unit, applying voltage only when needed for measurement cycles rather than continuously. This periodic operation maintains reliable PM detection capability while significantly reducing average power consumption compared to continuous voltage application.
Solution Approach 2:
The patent makes the bias voltage application dynamic by controlling it through a separate power supply unit that can adjust voltage application timing and duration. This dynamic control allows the system to apply voltage only when measurements are needed, optimizing the balance between detection reliability and energy consumption.
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 reduces sensor costs by eliminating the need for expensive switches and enhances sensitivity in PM detection by measuring capacitance simultaneously with bias voltage application, allowing for more accurate PM resistance monitoring.
Implementation Method 1
a detection unit forming a magnetic field by using detected voltage applied from the bias voltage and generating PM resistance by the PM by inducing the PM to the electric field
Implementation Method 2
a measurement unit including a first capacitor and a second capacitor in series and measuring the changed capacitance of the first capacitor and the second capacitor according to a change in PM resistance by connecting any one capacitor to the detection unit in parallel
Data Source
AI summary
In detecting a particulate matter (PM), which measures a change in capacitance depending on induction of the particulate matter, an apparatus for detecting a particulate matter includes: a power supply unit applying bias voltage for inducing the PM; a detection unit forming a magnetic field by using detected voltage applied from the bias voltage and generating PM resistance by the PM by inducing the PM to the magnetic field; and a measurement unit including a first capacitor and a second capacitor in series and measuring the changed capacitance of the first capacitor and the second capacitor according to a change in PM resistance by connecting any one capacitor to the detection unit in parallel. A method for detecting a particulate matter includes: applying bias voltage; generating PM resistance; and measuring changed capacitance according to a change in PM resistance by using the apparatus.