Inductive Detector With Variable Width Loops On Single-Layer PCB
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Solution Overview
Problem
Inductive detectors face limitations due to high manufacturing costs and limited measurement performance, particularly in extreme environments, where traditional methods require electrical connections and suffer from weak signal strengths, electromagnetic susceptibility, and low signal-to-noise ratios, making them unsuitable for mass market applications and precise measurements like light touch detection.
Innovation Solution
A high-performance, inexpensive inductive detector design featuring a microprocessor-controlled antenna with reduced capacitive coupling and minimal via holes, using a single-layer PCB with non-overlapping windings and a transformer for contactless power and signal transmission, enabling precise displacement measurement and identification of target objects without electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional inductive detectors use multi-layer PCBs with fine diameter plated via holes, then measurement precision can be improved, but manufacturing costs increase significantly
Solution Approach 1:
The patent removes via holes from the PCB structure entirely, extracting the problematic element that caused high manufacturing costs. The antenna windings are routed on the surface of a single-layer PCB without requiring plated through-holes, eliminating the expensive multi-layer construction while maintaining measurement precision through alternative winding geometries.
Solution Approach 2:
The invention uses inexpensive single-layer PCBs with simple copper trace windings instead of expensive multi-layer PCBs with fine plated via holes. This substitution of cheap, easily manufactured components achieves the same functional result without the high production costs associated with complex PCB structures.
2Measurement precision
If inductive detectors use higher power transmit signals to generate higher signal amplitudes, then signal strength is improved, but electromagnetic emissions increase excessively
Solution Approach 1:
The patent employs resonant oscillation at specific frequencies to amplify the electromagnetic signal without increasing transmit power. By tuning the antenna and EID to resonate at matching frequencies, the system achieves high signal amplitudes through resonant buildup rather than brute-force power injection, thereby avoiding excessive electromagnetic emissions.
Solution Approach 2:
The invention changes the frequency parameter of the transmit signal to match the resonant frequency of the EID, transforming the system from a high-power broadband transmitter to a low-power narrowband resonant system. This parameter adjustment enables high signal strength at the resonant frequency while minimizing emissions at other frequencies.
3Reliability
If conventional inductive detectors require electrical connections to moving and stationary parts, then power and data transmission are reliable, but the device complexity and susceptibility to electromagnetic interference increase
Solution Approach 1:
The patent replaces mechanical electrical connections with contactless inductive coupling. Power and data are transmitted wirelessly through electromagnetic fields between the antenna and EID, eliminating the need for sliding contacts, brushes, or cable connections to moving parts. This substitution reduces mechanical complexity while maintaining reliable power and communication.
Solution Approach 2:
The electromagnetic field serves as an intermediary medium to transfer power and data between the stationary antenna and the moving EID. This field-based intermediary replaces direct electrical contact, enabling reliable transmission without physical connections that would complicate the moving assembly.
4Measurement precision
If inductive detectors use complex antennae and EID constructions, then measurement precision can be improved, but manufacturing costs and device complexity increase
Solution Approach 1:
The patent segments the antenna system into simple planar windings on a stationary PCB and a separate simple EID on the moving part. Each component uses basic single-layer PCB construction with simple copper traces, avoiding complex multi-layer stacked windings. The segmentation allows each part to be manufactured independently using inexpensive processes while achieving precise measurement through their coordinated interaction.
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 solution provides a cost-effective, high-resolution inductive detector capable of precise displacement measurement and contactless power/data transmission, suitable for various environments, including aggressive conditions, with improved signal strength and reduced electromagnetic interference.
Implementation Method 1
The antenna typically contains transmit windings arranged along the axis of movement. An alternating electromagnetic field is formed around the transmit windings. When the EID enters this electromagnetic field, currents are induced to flow in its circuit.
Implementation Method 2
Alternatively a passive, unconnected EID may be used which, in turn, generates its own alternating electromagnetic field. This field induces a signal in the antenna's receive circuits which is indicative of the EID's position relative to the antenna.
Implementation Method 3
Higher signal strengths may be achieved by using electrically resonant EIDs. Resonant EIDs co-operating with an antenna are to be found in an automatic meter reading system
Data Source
AI summary
An inductive detector operable to measure relative displacement along a measurement path of a first body including an electrical intermediate device and a second body including at least three windings. At least one winding is a transmit winding and at least one other is a receive winding. The windings are arranged such that relative displacement of the two bodies causes a change in inductive coupling between at least one transmit winding and at least one receive winding. At least two windings are formed by a convoluted conductor with a first portion extending along the measurement path on a first surface of the substrate and a second portion returning back along the measurement path on an opposite second surface of the substrate. The first and second portions are connected via a connection extending between the first and second surfaces. Each convoluted conductor forms a series of loops defined between the portions on the first and second surfaces, the width of each loop varying along the measurement path and adjacent loops having opposite electromagnetic polarity. At least two windings are spaced in an axis normal to the measurement path.