Capacitance Detection Circuit Correcting Parasitic Charge Time
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Solution Overview
Problem
Capacitance components with large capacitance values on detection paths can interfere with the measurement of object capacitance, making it difficult to accurately detect variations in capacitance values.
Innovation Solution
A module with a current path and capacitance detecting circuit that supplies a constant current to both the object of detection and a capacitance component, using a storage unit for pre-measured data, a charge/discharge circuit, and a time measuring circuit to calculate the capacitance value based on charging times, allowing for accurate detection by correcting for variations in the capacitance component's influence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a capacitance component with large capacitance value is present on the detection path, then the detection circuit can be simplified, but the measurement precision deteriorates due to interference with the object capacitance measurement
Solution Approach 1:
The patent segments the total capacitance measurement into two separate measurements: first measuring the capacitance component (Cp) alone by disconnecting the object, then measuring the total capacitance (Cp + Cs) with the object connected. By subtracting the first measurement from the second, the system isolates the object capacitance (Cs) and eliminates the interference from the capacitance component. This segmentation approach resolves the contradiction by maintaining circuit simplicity while achieving precise measurement through separate measurement stages.
2Adaptability or versatility
If the capacitance component value varies device by device, then manufacturing adaptability improves, but measurement precision deteriorates as the variation becomes comparable to the detection target variation
Solution Approach 1:
The patent implements a feedback mechanism by measuring the capacitance component (Cp) in advance and storing this value. During subsequent object capacitance measurements, the stored Cp value is subtracted from the total capacitance reading to compensate for device-to-device variations in the capacitance component. This feedback approach allows the system to adapt to different Cp values across devices while maintaining precise measurement of object capacitance variations, thus resolving the contradiction between adaptability and precision.
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
Enables highly accurate detection of capacitance values by isolating and correcting for the capacitance component's effect, ensuring precise measurement of the object's capacitance.
Implementation Method 1
a constant current source supplying a constant current to a voltage detection point
Data Source
AI summary
A capacitance detecting circuit includes a constant current source supplying a constant current to a voltage detection point, a time measuring unit measuring time of charge until the voltage of the voltage detection point reaches a prescribed voltage, a storage unit and an operation unit. The storage unit stores first data obtained in advance concerning the time of charge of a capacitance element having a known capacitance value, and second data obtained in advance concerning the time of charge of a capacitance component. The operation unit generates third data representing the time of charge of an object of detection from a difference between the first measurement value of the time measuring unit when the capacitance component is connected to the voltage detection point and the second data, and based on the ratio between the third data and the first data and the known capacitance value, calculates the capacitance value of the object of detection.