Inductive Proximity Switch Oscillator With Switched Trim Resistance
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Solution Overview
Problem
Existing inductive proximity switches face challenges in reliably determining and adjusting the resonant impedance, which is crucial for setting the switching distance, as trimming resistors cannot be changed post-manufacturing, leading to inflexible operation and sensitivity to temperature variations.
Innovation Solution
An electronic switching device alternately switches a balancing resistor on and off, defining a time-average electrical resistance through a controlled switching sequence, allowing for continuous and monotonic adjustment of resonant impedance, thereby enabling flexible adjustment of the switching distance and reducing temperature influences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a trim resistor is used to adjust the resonant impedance, then the switching distance can be set within certain limits, but the adjustment cannot be changed after manufacturing
Solution Approach 1:
The patent applies the dynamics principle by replacing the static trim resistor with a dynamically controllable resistance element. The resistance value can be changed after manufacturing through electronic control, allowing the switching distance to be adjusted flexibly without physical modifications. This transforms a fixed manufacturing parameter into a dynamically adjustable operational parameter.
Solution Approach 2:
The patent implements parameter changes by controlling the resistance value of the balancing resistor through electronic means. By changing the resistance parameter dynamically, the resonant impedance and consequently the switching distance can be adjusted after manufacturing. This allows the system to adapt to different requirements without physical reconfiguration.
2Manufacturing precision
If the resonant impedance is precisely adjusted to set the switching distance, then the oscillator operation is well-defined, but the system becomes sensitive to temperature variations
Solution Approach 1:
The patent applies feedback by continuously monitoring the oscillator's performance and adjusting the balancing resistor value to compensate for temperature-induced changes. The control system detects deviations from the desired resonant impedance caused by temperature variations and automatically adjusts the resistance to maintain the correct switching distance, thereby reducing temperature sensitivity while preserving manufacturing precision.
3Adaptability or versatility
If an electronic switching device is used to alternately switch the balancing resistor, then continuous adjustment of resonant impedance is enabled, but the device complexity increases
Solution Approach 1:
The patent merges the functions of the balancing resistor and the switching device into an integrated resistance adjustment mechanism. By combining these elements, the patent achieves continuous adjustment of the resonant impedance while minimizing the increase in device complexity. The merged structure allows for smooth resistance variation without requiring multiple discrete components.
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 allows for reliable and adjustable resonant impedance determination, maintaining consistent oscillator performance with minimal component count, reducing temperature dependencies and enabling post-manufacturing adjustments, thus enhancing the flexibility and reliability of inductive proximity switches.
Implementation Method 1
An electronic switching device alternately switches a balancing resistor on and off, defining a time-average electrical resistance through a controlled switching sequence
Implementation Method 2
a resonant circuit with at least one inductor and one capacitance
Implementation Method 3
a detection signal for a target to be detected is generated by evaluating the damping of the oscillator by the target to be detected, in particular a metallic target
Data Source
Figure 1
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Figure 4
AI summary
The invention relates to an oscillator comprising a resonant circuit having at least one inductor and one capacitor and having a feedback amplifier, wherein there is at least one trimming resistor in a feedback circuit of the amplifier. The oscillator is characterized in that there is an electronic switching device for alternately connecting and disconnecting the trimming resistor, in that a trimming circuit is formed by the trimming resistor and the electronic switching device, in that there is a drive device for driving the electronic switching device, in that the electronic switching device, together with the drive device, is designed to alternately connect and disconnect the trimming resistor in a switching sequence, and in that an average time value of the electrical resistor of the trimming circuit, which is active in an oscillator mode, is defined by the switching sequence.