Washing Bath Conductivity Sensing With Capacitive Galvanic Isolation
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Solution Overview
Problem
Existing electrical conductivity sensing devices for washing machine baths are cumbersome and costly due to the use of transformers for signal coupling and galvanic isolation.
Innovation Solution
The use of capacitors in series between electrodes and circuit terminals provides galvanic isolation and coupling, allowing for a more compact and cost-effective design, with optional integration of a microprocessor for signal processing and a turbidity detection system, and additional electrodes for liquid level sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer is used for signal coupling and galvanic isolation, then reliable electrical insulation is achieved, but the device becomes cumbersome and costly
Solution Approach 1:
The patent changes the fundamental parameter of isolation implementation from magnetic coupling (transformer) to electrical coupling through capacitors. This parameter change allows achieving galvanic isolation with much smaller components while maintaining the required electrical insulation, directly resolving the contradiction between reliability of isolation and device complexity
Solution Approach 2:
The invention extracts the essential function of galvanic isolation from the complex transformer structure and implements it through simple capacitors. By taking out only the necessary isolation function and implementing it with minimal components, the device achieves reliable isolation without the cumbersome size and cost of a full transformer
2Reliability
If a transformer is used for signal coupling and galvanic isolation, then electrical insulation is maintained, but manufacturing cost increases
Solution Approach 1:
The patent changes the implementation parameter from magnetic coupling components to electrical coupling components (capacitors). This parameter change dramatically reduces manufacturing cost while maintaining galvanic isolation, as capacitors are much cheaper and easier to manufacture than transformers with the required isolation specifications
3Measurement precision
If conventional sensing devices are used, then conductivity measurement is achieved, but additional features like turbidity detection and level sensing require separate devices
Solution Approach 1:
The patent implements universality by designing a multi-functional sensing device that combines conductivity measurement, turbidity detection, and liquid level sensing into a single integrated system. The microprocessor controls multiple sensors and performs various measurements, allowing the device to adapt to different monitoring needs without requiring separate devices for each function
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 solution reduces the size and cost of the sensing device while maintaining effective conductivity measurement and enabling additional features like turbidity detection and liquid level monitoring, with improved interference rejection and modest current injection.
Implementation Method 1
the aforesaid galvanic isolation and coupling means comprise at least a first and a second capacitor, each of which is inter interconnected in series between one of said electrodes and a corresponding terminal of the aforesaid circuit means
Implementation Method 2
first and second electrodes, intended to contact the liquid
Implementation Method 3
a device for detecting the turbidity of the washing bath, comprising a photoemitter and a photodetector facing one another
Data Source
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AI summary
The device (1) comprises an electrically insulating supporting casing (2) through which first and second electrodes (A, B) intended to contact the washing bath extend to the outside, electrical power supply and signal acquisition and processing circuit devices (4) housed at least in part in the supporting casing (2) and coupled to the electrodes (A, B), and signal coupling and galvanic isolation devices, interposed between these circuit devices (4) and the electrodes (A, B) and also housed in the casing (2), and comprising at least a first and a second capacitor (C), each of which is interconnected in series between one of the electrodes (A, B) and a corresponding terminal (9, 10) of the circuit means (4).