Inductive Proximity Switch Circuit With Reference Coil Self-Check
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Solution Overview
Problem
Existing inductive approximation switches do not reliably detect errors in electrical components and have varying switching distances for different metallic materials, limiting their usability and safety in applications.
Innovation Solution
The solution involves assigning a reference coil to the vibration circuit, connecting it in parallel with the transmission coil, and using a logic channel with switches to alternately control the transmission and reference coils. This allows for continuous monitoring of the electrical components and ensures a consistent switching distance across different metallic materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single transmitting coil is used for proximity detection, then the device structure is simple, but the switching distance varies significantly for different metallic materials
Solution Approach 1:
The single transmitting coil is segmented into two separate coils: a first transmitting coil for generating the primary magnetic field and a second transmitting coil for generating a reference signal. This segmentation allows the system to differentiate between material-induced changes and system variations, enabling consistent switching distance measurement across different metallic materials while maintaining a manageable device structure.
Solution Approach 2:
A reference coil (second transmitting coil) is introduced as an intermediary element that provides a baseline reference signal unaffected by the presence of metallic objects. By comparing the signal from the first transmitting coil against this reference, the system can accurately detect proximity while compensating for material property variations, thus achieving consistent switching distance across different metals.
2Reliability
If traditional proximity switch components are used, then the device is compact, but component failures cannot be reliably detected
Solution Approach 1:
The system performs preliminary self-diagnosis by continuously monitoring the oscillation states of both transmitting coils and evaluating whether they meet predetermined criteria. This preliminary action detects component failures before they cause system malfunction, ensuring reliable operation while integrating the diagnostic function into the existing circuit structure without significant complexity increase.
Solution Approach 2:
A feedback mechanism is implemented where the evaluation unit continuously monitors the oscillation signals from both transmitting coils and compares them against predetermined conditions. When deviations indicate component failure, the system generates appropriate responses (warnings or shutdowns), creating a closed-loop feedback system that enhances reliability while maintaining circuit compactness through intelligent signal processing.
3Reliability
If the proximity switch operates continuously, then productivity is maintained, but undetected component failures may lead to safety issues
Solution Approach 1:
The system performs preliminary self-diagnosis during normal continuous operation by continuously monitoring oscillation states and comparing them against predetermined criteria. This allows the system to maintain productivity while proactively detecting component failures before they compromise safety, enabling early intervention without interrupting operational flow.
Solution Approach 2:
The self-diagnosis function operates continuously alongside the proximity detection function, with both transmitting coils oscillating simultaneously and being monitored in real-time. This continuous dual-function operation ensures that safety monitoring does not interrupt productivity, as the diagnostic process is integrated into the normal operational cycle rather than requiring separate testing periods.
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 approach ensures reliable detection of component errors and maintains a consistent switching distance, enhancing the safety and usability of the approximation switch in various applications.
Implementation Method 1
an oscillating circuit 2 in which a transmitting coil 3, a capacitor 4, and an oscillator 5 are connected
Implementation Method 2
a reference coil 11 connected in parallel to the transmitting coil 3
Implementation Method 3
an LC circuit for exciting the transmitting and reference coils, respectively
Data Source
Figure 1a
Figure 1b
Figure 2
AI summary
For an electrical circuit forming an inductively operated proximity switch (1), consisting of a resonant circuit (2) in which a transmitting coil (3), a capacitor (4), and an oscillator (5) exciting the transmitting coil (3) are connected in parallel, a downstream evaluation unit (6) by which the amplitude (A) and frequency (F) of the resonant circuit (2) can be detected, a monitoring area (9) assigned to the transmitting coil (3) in which an object (10) located therein extracts energy from the resonant circuit (2), whereby a change in frequency (ΔF) and/or amplitude (ΔA) of the resonant circuit (2) can be detected in the evaluation unit (6) and is convertible into a switching signal, and a switch (7) arranged between the transmitting coil (3) and the evaluation unit (6), which is switched into an open and a closed switching position (So, Sg) by the evaluation unit (6) is transferableThe electrical circuit must be adaptable to all types of metallic materials without significantly altering the switching distance of the proximity switch (1) due to differing material properties. Furthermore, the electrical components forming the proximity switch (1) must be reliably monitored or checked permanently or at least intermittently to ensure their proper functioning and, consequently, reliable switching distance measurement. This is achieved by assigning a reference coil (11) to the resonant circuit (2), which is connected in parallel to the transmitting coil (3) and the oscillator (5). The reference coil (11) is connected to a logic channel (12), and at least one switch (131, 132...) is provided between the reference coil (11) and the logic channel (12), which is opened or closed by the evaluation unit (6) and/or the logic channel (12).and that data sets are stored and/or programmable in the logic channel (12) of the reference coil (11) by which the functioning of the resonant circuit (2) can be checked on the basis of specified frequencies (F) and/or amplitudes (A).