Inductive Proximity Sensing Using Full Pulse Digitization
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Solution Overview
Problem
Inductive proximity sensors face challenges in achieving high switching distances and factor 1 behavior for various metallic objects, especially in harsh environments, and are often limited by their sensor housings and installation precision.
Innovation Solution
The solution involves digitizing the voltage pulse from the transmission current pulse to the complete decay of the voltage pulse, using a dual coil configuration with optimized winding ratios, and employing a control and evaluation unit that analyzes sampling values with increased temporal resolution and filtering to distinguish and classify objects, while being housed in a metallic enclosure for mechanical robustness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the sensor uses a conventional design with metal housing and plastic front face, then the manufacturing is simplified, but the switching distance is reduced and factor 1 behavior is not achieved
Solution Approach 1:
The patent changes the material parameter of the housing from conventional metal to plastic, and modifies the front face structure by integrating a metal screen directly into the plastic housing. This parameter change enables factor 1 behavior across different metal types while maintaining manufacturing simplicity through injection molding with embedded metal screens.
Solution Approach 2:
The sensor housing combines plastic material with an integrated metal screen in a composite structure. The plastic housing provides mechanical protection and electrical insulation, while the metal screen enables electromagnetic field penetration for detecting non-ferrous metals, achieving both extended switching distance and factor 1 behavior.
2Measurement precision
If the sensor switching distance is increased, then the installation tolerance is improved and mechanical damage risk is reduced, but the sensor diameter must be increased
Solution Approach 1:
The patent changes the evaluation parameter from conventional threshold-based detection to digital signal evaluation with artificial neural networks. This enables the system to extract more information from the voltage pulse, achieving extended switching distance without proportionally increasing the sensor diameter.
Solution Approach 2:
The patent replaces conventional analog signal processing with digital signal evaluation and artificial neural networks. This substitution enables more efficient extraction of object information from the voltage pulse, achieving longer switching distance without increasing sensor physical dimensions.
3Loss of information
If the voltage pulse is digitized from transmission current pulse to complete decay, then the information content is maximized and object classification is enabled, but the processing complexity increases
Solution Approach 1:
The patent replaces conventional analog signal processing with digital signal evaluation using an artificial neural network. The entire voltage pulse from transmission current pulse to complete decay is digitized and processed, maximizing information content while the neural network efficiently handles the processing complexity through learned patterns.
Solution Approach 2:
The patent introduces an artificial neural network as an intermediary between the digitized voltage pulse and the object classification output. The neural network processes the complete pulse information and translates it into meaningful object classification, managing the complexity of analyzing the entire voltage pulse waveform.
4Measurement precision
If a single coil is used for transmission and reception, then the device complexity is reduced, but the signal-to-noise ratio and switching distance are limited
Solution Approach 1:
The patent segments the coil system into separate transmitting and receiving coils. The transmitting coil generates the excitation pulse while the receiving coil detects the voltage pulse from the object, reducing electromagnetic interference and improving signal-to-noise ratio compared to a single coil configuration.
Solution Approach 2:
The patent extracts the reception function from the transmission coil by using a separate receiving coil. This separation allows the receiving coil to be optimized for detecting weak voltage pulses from objects without being contaminated by the strong transmission signal, improving overall system performance.
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 enhances the switching distance, reduces mechanical damage risk, allows for greater installation tolerance, and enables miniaturization, while accurately differentiating metallic objects and providing robustness against environmental factors.
Implementation Method 1
at least one transmission current pulse is applied to the coil (3) and a control and evaluation unit (7) for outputting an object detection signal (8)
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
Method and inductive proximity sensor for detecting an object (2), with at least one coil (3), at least one transmission current pulse being able to be applied to the coil by a control and evaluation unit (7), and the control and evaluation unit (7) for output an object detection signal (8), wherein the control and evaluation unit (7) is designed to emit at least one induced voltage pulse (9), which is generated by the transmission current pulse at the coil (3), in at least one section from or after the time of application of the transmission current pulse until the voltage pulse (9) has completely decayed and to form sampled values (10), whereby the voltage pulse (9) is digitized, the control and evaluation unit (7) being designed to determine the distance of a metallic object (2) to evaluate the samples (10) of at least two voltage pulses (9).