Inductive Sensor with Segmented Coils for Metal Type Detection
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Solution Overview
Problem
Existing inductive proximity sensors are limited in detecting both ferrous and non-ferrous metals and are not operational in constant or alternating magnetic fields of industrial frequency, lacking the ability to differentiate between metal types and requiring physical connection with the target.
Innovation Solution
An inductive proximity sensor using an air-core transformer arrangement with a primary and secondary coil, an operational amplifier, and signal processing means, including low-stop filters to suppress noise, generates distinct signals for ferrous and non-ferrous targets, allowing differentiation and operation in industrial magnetic fields without physical contact.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional inductive sensor uses a single coil to detect metal targets, then it can detect ferromagnetic materials, but it cannot detect or differentiate non-ferrous metals
Solution Approach 1:
The sensor divides the detection function into two separate coils: a first coil for detecting ferromagnetic targets and a second coil for detecting non-ferrous metal targets. Each coil is optimized for its specific detection purpose, allowing the sensor to differentiate between metal types without requiring a single complex detection mechanism.
Solution Approach 2:
The sensor achieves multi-functionality by combining two coils with different detection capabilities into a single sensor unit. The first coil handles ferromagnetic detection while the second coil handles non-ferrous metal detection, making the overall sensor universal in detecting both metal types.
2Reliability
If the sensor uses a standard inductive coil design, then it has simple structure, but it cannot operate in constant or alternating magnetic fields of industrial frequency
Solution Approach 1:
The sensor introduces intermediary components including low-stop filters and signal processing circuits that act as mediators between the coils and the output signals. These intermediaries suppress industrial frequency magnetic field interference and process the raw coil signals into usable detection outputs, enabling reliable operation in industrial environments.
Solution Approach 2:
The sensor employs feedback mechanisms through signal processing means that continuously monitor and adjust the detection signals. The low-stop filters provide feedback to suppress noise at industrial frequencies, and the signal processing circuits use feedback to maintain accurate detection despite magnetic field interference.
3Ease of operation
If the sensor requires physical connection with the target for detection, then the detection mechanism is simple, but it cannot detect targets without contact
Solution Approach 1:
The sensor replaces mechanical contact-based detection with electromagnetic field-based detection. The coils generate magnetic fields that interact with metal targets at a distance, inducing eddy currents in the targets without physical contact. This substitution of mechanical detection with electromagnetic detection enables non-contact operation while maintaining detection sensitivity.
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 sensor effectively detects and differentiates between ferrous and non-ferrous targets, maintaining functionality in industrial magnetic fields, and can be flush-mounted, providing accurate position and material information without physical connection.
Implementation Method 1
When the coil with its associated flux field is placed close to the conductive target, the field establishes electric currents in the target. These currents are eddy currents, i.e. closed loops of induced current circulating (in a direction opposite to the current in the coil) in planes perpendicular to the magnetic flux
Implementation Method 2
an air-core transformer arrangement with a primary and secondary coil
Data Source
Figure 1~2
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AI summary
The present invention relates to an inductive presence or position sensor. Inductive sensor or detector of the type comprising as its sensitive element, preferably defining a front working plane of the sensor, a coil system forming an air-core transformer arrangement with a primary coil or winding and a secondary coil or winding, said primary coil or winding of said system being associated with a capacity component in order to constitute a LC oscillating circuit whose oscillation is sustained by an adapted generator in the form of an operational amplifier and an associated resistance arrangement, the sensor also comprising signal processing means, for example signal adding, amplifying, converting and/or evaluating circuits, fed by at least one signal provided by at least one component of the coil system, inductive sensor (1) characterised in that it comprises a direct or indirect feedback line (11) from the secondary coil or winding (3) to the input of the operational amplifier (6) of the generator (5).