Differential Capacitive Sensing for Detergent Type Detection
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Solution Overview
Problem
Capacitive sensing devices face challenges in accurately detecting conductive substances like detergent due to environmental factors such as temperature and humidity, leading to false detections and performance issues across varying temperature ranges.
Innovation Solution
A differential capacitive sensing system with two capacitive sensors and a processing device that measures and compares capacitance changes to distinguish between different types of conductive substances, such as powder and gel detergents, by accounting for environmental effects and using a method to determine the presence and type of material based on capacitance increases within specific thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single capacitive sensor is used to detect conductive substances, then the device structure is simple, but the detection accuracy is reduced due to environmental factors such as temperature and humidity
Solution Approach 1:
The system divides the detection function into two separate capacitive sensors: a first capacitive sensor for detecting conductive substances and a second capacitive sensor for detecting environmental factors. This segmentation allows each sensor to specialize in one type of detection, improving overall measurement precision while maintaining reasonable device complexity.
Solution Approach 2:
The second capacitive sensor acts as an intermediary that measures environmental factors (temperature and humidity effects) which then serve as reference data for compensating the measurements from the first sensor. This intermediary approach enables the system to account for environmental interference without requiring the primary sensor to directly measure both targets and environmental factors.
2Ease of operation
If capacitive sensing is used to detect conductive substances, then non-contact detection is achieved, but false detections occur due to temperature drift affecting sensor capacitance
Solution Approach 1:
The system implements feedback by continuously monitoring environmental factors with the second capacitive sensor and using this information to adjust and compensate the readings from the first sensor. The processing device uses the reference data from the second sensor to correct temperature drift effects, thereby maintaining reliable detection despite environmental variations.
Solution Approach 2:
The patent converts the harmful effect of temperature drift into a useful measurement signal. By using the second capacitive sensor to specifically measure the temperature-induced capacitance changes, the system transforms the environmental interference into reference data that can be used to correct and improve the accuracy of the primary detection, turning a source of error into a tool for compensation.
3Reliability
If compensation for temperature drift is implemented, then detection reliability is improved, but device complexity increases
Solution Approach 1:
The system merges the environmental sensing function with the existing capacitive sensing architecture by using a second capacitive sensor that operates on the same physical principle as the first sensor. This allows the system to implement temperature compensation without introducing fundamentally different sensor technologies or complex compensation mechanisms, thereby limiting the increase in device complexity.
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 system effectively differentiates between different materials by accurately measuring capacitance changes, reducing false detections and ensuring reliable operation across a wide temperature range, thereby enhancing the performance of appliances that use capacitive sensing for detergent detection.
Implementation Method 1
A capacitance sensing device includes an array of one or more capacitive sensors. The capacitance detected by a capacitive sensing device changes as a function of the proximity of a conductive object or substance to the device.
Implementation Method 2
changes in ambient temperature will affect the capacitance detected by the sensors because the self-capacitance of the sensors changes with temperature. In general, the capacitance detected by the sensors changes linearly with changes in temperature.
Data Source
AI summary
A method and apparatus to detect the presence of a material at a sensing device and to determine whether the material is a first material having a first material property or a second material having a second material property.