Coin Sensor Multi-Frequency Inductive Bridge for Counterfeit Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing coin recognition technologies using inductive sensors face limitations in accurately measuring multi-layer coins due to reliance on single-frequency operations, lack of individual inductor impedance measurements, and excessive complexity, which hinders reliable discrimination between genuine and counterfeit coins.
Innovation Solution
A coin sensor employing two inductors arranged facing each other, with each inductor forming part of an independent bridge, excited by a pattern signal (multi-tone, broadband, or variable signal) to measure both individual and mutual impedances, enabling calculations in in-phase, out-of-phase, and emitter-receiver modes, and utilizing a transimpedance amplifier for improved signal/noise ratio and frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single-frequency signal is used to excite the inductor, then the device complexity is reduced, but the measurement precision of multi-layer coin characteristics deteriorates
Solution Approach 1:
The patent applies periodic action by using a multi-frequency periodic signal to excite the inductor, allowing measurements at multiple frequencies (including fundamental and harmonic frequencies) to be obtained simultaneously. This enables comprehensive characterization of multi-layer coins without requiring multiple separate measurements, thus improving measurement precision while maintaining relatively simple device operation.
Solution Approach 2:
The patent changes the frequency parameter of the excitation signal to include multiple frequencies rather than a single frequency. By analyzing the response at different frequencies (fundamental and harmonics), the system obtains deeper information about the coin's multi-layer structure, resolving the contradiction between simple excitation and precise measurement.
2Device complexity
If only emitter-receiver mode is used, then the device complexity is reduced, but the reliability of coin discrimination deteriorates
Solution Approach 1:
The patent implements multi-functionality by enabling the inductor to operate in multiple modes (emitter-receiver mode and in-phase mode) using the same hardware configuration. The system can switch between modes or combine measurements from both modes to improve coin discrimination reliability without requiring separate dedicated hardware for each mode.
Solution Approach 2:
By using periodic multi-frequency excitation, the system can extract different types of information from the same measurement cycle, enabling both emitter-receiver and in-phase mode measurements to be performed systematically, thereby improving reliability without increasing operational complexity.
3Measurement precision
If multi-frequency signal with high harmonic content is used, then the measurement precision of coin structure is improved, but the loss of information in individual inductor impedance measurements increases
Solution Approach 1:
The patent applies feedback by measuring and analyzing the impedance response at multiple frequencies including harmonics, then using this information to compensate for and remove the influence of individual inductor characteristics. This allows the system to extract accurate coin structure information while eliminating the confounding effect of inductor impedance variations.
Solution Approach 2:
By changing the frequency parameter to include multiple frequencies and harmonics, the system obtains sufficient information to separate and remove the inductor's individual impedance contribution from the measurement, thereby recovering the lost information about individual inductor characteristics while maintaining high measurement precision for coin structure.
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 configuration allows for secure identification of coins by providing maximum information on conductivity, magnetic permeability, and structural characteristics, enhancing the reliability of coin recognition and rejection of counterfeit coins, particularly for multi-layer coins.
Implementation Method 1
The inductors are formed by one or more coils that are introduced in a magnetic core to increase the intensity of the magnetic flow that reaches the coin and the opposing inductor
Implementation Method 2
The depth of penetration of the field generated by the inductors decreases as their frequency increases and, likewise, decreases when the conductivity of the coin or its magnetic permeability increases
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A coin sensor (100; 200; 300; 400) comprising a first inductive branch (113; 213; 313; 413) with a first inductor (112; 212; 312; 412) in series with a first resistor (114; 214; 314; 414); a second inductive branch (123; 223; 323; 423) with a second inductor (122; 222; 322; 422) in series with a second resistor (124; 224; 324; 424), wherein the first (112; 212; 312; 412) and second (122; 222; 322; 422) inductors are arranged facing each other on both sides of a passage channel (102) of coins (104) to be discriminated; at least one capacitive branch with a condenser (118, 128; 218, 228; 318; 418) and a resistor (116, 126; 216, 226; 316; 416) in series; an excitation circuit with a generator (150;250;350;450) and at least one pair of switches (117, 127; 217,227; 317,327; 417,427), configured to alternately feed the first inductive branch (113; 213; 313; 413) and the second inductive branch (123; 223; 323; 423) with a pattern signal with spectral energy in two or more frequencies, such that the branch of the inductor excited at any given time is arranged in a bridge configuration with at least one capacitive branch; at least one differential amplifier (130,140; 230,240; 330; 430) configured to alternately measure the voltage between the exit nodes of the excited bridge.