Variable-Capacitance Sensing Circuit for Fast Low-Noise Detection
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Solution Overview
Problem
Existing capacitance detection devices face challenges in improving detection accuracy while minimizing the impact of low-frequency noise and power supply fluctuations, as increasing the number of switch manipulations to enhance accuracy can lead to reduced detection accuracy and longer detection times.
Innovation Solution
A capacitance detection device featuring a variable capacitance capacitor and a control circuit that manipulates the capacitance to control an intermediate potential to a reference potential, using a capacitor array with capacitors of different values and a differential amplifier to detect capacitance based on the ratio of detection and combined capacitance, allowing for faster and more accurate measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of switch manipulations is increased to improve detection accuracy, then measurement precision improves, but detection time increases and low-frequency noise influence becomes remarkable
Solution Approach 1:
The control circuit performs initialization processing before the main detection process, setting the initial state of capacitors and switches to ensure accurate detection from the start. This preliminary setup enables the detection to proceed efficiently without requiring excessive manipulation cycles
Solution Approach 2:
The control circuit monitors the intermediate potential during the detection process and uses this feedback information to determine when to terminate the switch manipulations. By detecting when the intermediate potential stabilizes or reaches a predetermined state, the system can stop the process early, avoiding unnecessary manipulation cycles while maintaining detection accuracy
2Measurement precision
If the number of switch manipulations is increased to improve detection accuracy, then measurement precision improves, but the influence of low-frequency noise and power supply fluctuations increases
Solution Approach 1:
The control circuit performs initialization processing before the main detection process, setting the initial state of capacitors and switches to ensure accurate detection from the start. This preliminary setup enables the detection to proceed efficiently without requiring excessive manipulation cycles
Solution Approach 2:
The control circuit monitors the intermediate potential during the detection process and uses this feedback information to determine when to terminate the switch manipulations. By detecting when the intermediate potential stabilizes or reaches a predetermined state, the system can stop the process early, avoiding unnecessary manipulation cycles while maintaining detection accuracy
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 the time required for capacitance detection, enhances accuracy, and minimizes the influence of low-frequency noise, allowing for higher resolution and lower costs by using a binary search method to quickly converge on the correct capacitance values.
Implementation Method 1
a variable capacitance capacitor; an electrode constituting a detection target whose capacitance is to be detected; and a control circuit, in which the control circuit executes: manipulation processing of manipulating a capacitance of the variable capacitance capacitor to control an intermediate potential
Data Source
AI summary
A capacitance detection device includes: a variable capacitance capacitor; an electrode constituting a detection target whose capacitance is to be detected; and a control circuit, in which the control circuit executes: manipulation processing of manipulating a capacitance of the variable capacitance capacitor to control an intermediate potential, which is a potential at a connection point between the variable capacitance capacitor and the electrode, to a reference potential, when a voltage of a voltage application device is applied to the electrode via the variable capacitance capacitor; and detection processing of detecting the capacitance of the detection target, based on the capacitance of the variable capacitance capacitor when being controlled to the reference potential.