Electronic Switch Buffering Mechanical Contact Impedance
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Solution Overview
Problem
Conventional mechanical switches are prone to failure due to contact wear, galling, fretting, contact welding, and contamination, leading to high impedance issues that can result in false open states, which are not indicative of the intended pressure measurements in applications like pressure switches.
Innovation Solution
An electronic switch device is coupled to mechanical switches, utilizing a gain device with a transistor and resistor configuration to sense contact impedance and represent it as a constant or low impedance to an external circuit, effectively compensating for variations in contact impedance and reducing the effects of wear, contamination, and contact bounce.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanical switch is used to provide metal contact closure, then the switch can open or close electrical contact, but contact wear, galling, fretting, and contamination lead to high impedance and false open states over time
Solution Approach 1:
The patent introduces an electronic switch circuit as an intermediary between the mechanical switch and the external circuit. This electronic circuit senses the contact impedance of the mechanical switch and provides a buffered output that is independent of the mechanical contact impedance variations, thereby protecting the external circuit from the harmful effects of contact wear and contamination
Solution Approach 2:
The patent replaces the direct mechanical contact connection with an electronic sensing and buffering system. Instead of relying on the mechanical switch's contact impedance to directly control the external circuit, an electronic circuit with high input impedance and low output impedance is used to sense and reproduce the switch state, eliminating the harmful effects of mechanical contact degradation
2Ease of operation
If mechanical switch contacts are used, then the switch can function, but contact impedance variations due to wear and contamination cause false failures
Solution Approach 1:
The electronic switch circuit acts as an intermediary that decouples the mechanical switch operation from the external circuit. It senses the contact impedance and provides a clean digital output that accurately represents the switch state without being affected by contact impedance variations, thereby ensuring accurate pressure measurements
Solution Approach 2:
The patent creates an electronic copy or representation of the mechanical switch state through the electronic circuit. The circuit senses the contact impedance and generates a buffered output signal that copies the switch state information while eliminating the noise and variations caused by contact wear and contamination
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 electronic switch extends the life expectancy of mechanical switches by two to twenty times, maintaining a consistent impedance and preventing false failures, ensuring accurate pressure indications in high-vibration environments.
Implementation Method 1
the gain device may include a transistor device with a current gain such that the contact impedance of the switch appears lower than the sensed actual contact impedance of the switch
Data Source
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AI summary
A device (11), including: a sensor circuit (15) that senses the state of contact impedance of a mechanical electrical switch (12); and a switch-off circuit (13) that represents a sensed high impedance contact of the switch as a low or constant impedance, where the sensor circuit (15) detects an open or closed condition of the switch (12) by sensing a voltage across the switch passing a threshold value.