Capacitive Proximity Sensor Distinguishing Human Body and Water
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Solution Overview
Problem
Capacitive proximity sensors struggle to reliably distinguish between a human body and water, as existing systems rely on changes in resonance voltage or frequency that can be influenced by environmental factors and circuit constants, leading to difficulties in differentiation.
Innovation Solution
A capacitive proximity sensor with an LCR resonance circuit and a control unit that adjusts the high-frequency signal to ensure distinct resonance frequencies and voltage signals for human body and water detection, maintaining these differences across varying environmental temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If resonance voltage changes are used to detect object proximity, then detection capability is achieved, but ability to distinguish between different objects (human body vs water) is insufficient
Solution Approach 1:
The patent transitions from single-parameter resonance voltage detection to two-dimensional detection using both resonance voltage and resonance frequency. By adding frequency as a second dimension of measurement, the system can distinguish between human bodies and water, which have different effects on the resonance characteristics of the sensor electrode.
Solution Approach 2:
The patent monitors changes in both resonance voltage and resonance frequency parameters when objects approach the sensor electrode. Different objects (human body vs water) cause different patterns of parameter changes, enabling reliable differentiation through comparative analysis of these parameter variations.
2Measurement precision
If output frequency or time changes are used to distinguish human bodies from water, then differentiation capability is improved, but reliability under varying environmental conditions (temperature) and circuit constants deteriorates
Solution Approach 1:
The patent uses the relationship between resonance frequency and capacitance changes to distinguish objects. By analyzing how resonance frequency shifts in response to capacitance changes caused by different objects, the system achieves reliable differentiation that is less sensitive to environmental temperature variations and circuit constant changes.
Solution Approach 2:
The system continuously monitors the resonance characteristics and uses the relationship between frequency and voltage changes as a feedback mechanism to identify object type. This feedback approach allows the system to adapt to environmental variations while maintaining accurate object differentiation.
3Stability of the object's composition
If excitation frequency is set higher than resonance frequency to ensure voltage decrease, then detection consistency is improved, but ability to distinguish between different objects deteriorates
Solution Approach 1:
The patent adds resonance frequency measurement as a second dimension to the detection system. While resonance voltage alone provides consistent detection signals, the addition of frequency information enables object type discrimination, as different objects produce different frequency responses even when voltage changes follow similar patterns.
Solution Approach 2:
The system analyzes changes in both resonance voltage and resonance frequency parameters simultaneously. By examining the combined pattern of parameter changes rather than relying solely on voltage decrease, the system maintains detection consistency while achieving the ability to distinguish between different objects.
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
The solution allows for reliable differentiation between human body and water proximity by controlling the high-frequency signal to maintain consistent and opposite direction changes in determination voltage signals, effectively distinguishing between the two even with temperature variations.
Implementation Method 1
a sensor circuit, having an LCR resonance circuit, including a sensor electrode, into which the high-frequency signal is input, and which outputs a determination voltage signal in accordance with the capacitance of the sensor electrode
Implementation Method 2
capacitive proximity sensor which detects the proximity or contact of a human body (hand or the like)... detect the proximity of an object on the basis of changes in the capacitance of a sensor electrode
Data Source
AI summary
The resonance frequency of an LCR resonance circuit is f1 and the determination voltage signal is V1, when an object is not in the proximity of a sensor electrode. The resonance frequency of the LCR resonance circuit is f2 and the determination voltage signal is V2, when a human body is in proximity of the sensor electrode 22. The resonance frequency of the LCR resonance circuit is f3 and the determination voltage signal is V3, when water is in the proximity of the sensor electrode. The LCR resonance circuit has the relationship f1>f2>f3. A control unit controls a high-frequency signal S0 so as to satisfy the relationship V2>V1>V3, and a human body or water being in the proximity of the sensor electrode is distinguished.