Metal Detector Signal Sampling Without Synchronous ADC Timing
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Solution Overview
Problem
Existing metal detectors face challenges with false alarms due to ferromagnetic components in soil and require improved frequency selection and asynchronous sampling to accurately analyze analog signals without additional electronic components, which are costly and prone to performance variations.
Innovation Solution
The method employs asynchronous sampling using a high-resolution ADC to analyze signals with minimal error, eliminating the need for synchronization and allowing frequency selection independent of the sampling period, using dynamic coefficients and pre-determined time intervals for accurate phase and magnitude calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If synchronous sampling is used to accurately analyze signals, then signal analysis accuracy is improved, but device complexity increases due to additional electronic components and synchronization requirements
Solution Approach 1:
The patent extracts the synchronization function from the sampling system by using pre-stored sine and cosine coefficient tables that correspond to signal frequency. Instead of requiring complex electronic synchronization components, the system separates the timing reference function into lookup tables, allowing asynchronous ADC sampling while maintaining accurate phase and magnitude calculation through coefficient-based correction.
Solution Approach 2:
The patent replaces the mechanical/electronic synchronization system with a digital lookup table system. Instead of using synchronous switches and timing circuits to coordinate ADC sampling with signal frequency, the system uses pre-calculated sine and cosine coefficient tables stored in memory, substituting complex hardware synchronization with simpler digital memory access and multiplication operations.
2Measurement precision
If synchronous sampling is used to ensure accurate phase and magnitude calculation, then measurement precision is improved, but the ADC selection range is limited due to frequency-matching requirements
Solution Approach 1:
The patent introduces dynamic adaptability by making the sine and cosine coefficient tables frequency-dependent. The system can dynamically select or generate appropriate coefficient tables based on the detected signal frequency, allowing the ADC to operate asynchronously at any frequency while maintaining accurate phase and magnitude calculations through frequency-matched coefficient selection.
Solution Approach 2:
The patent changes the approach from fixed synchronous sampling to asynchronous sampling with parameter correction. By storing multiple sets of sine and cosine coefficients corresponding to different signal frequencies and selecting the appropriate set based on detected frequency, the system allows ADC frequency independence while maintaining measurement accuracy through parameter (coefficient) adjustment.
3Reliability
If multiple frequency options are provided for discriminating metallic targets, then false alarm rate decreases, but device complexity increases due to frequency selection mechanisms
Solution Approach 1:
The patent implements multi-functionality by using a single ADC and coefficient table system that can handle multiple signal frequencies. Instead of requiring separate sampling systems for each frequency, the universal coefficient tables allow the same hardware to accurately process signals at any frequency by selecting the appropriate coefficient set, enabling frequency discrimination without additional complex selection mechanisms.
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 signal analysis accuracy, reduces false alarms, and enables the use of cost-effective ADCs, providing wider selection and improved performance across various frequencies.
Implementation Method 1
The voltage source that switched by the switching component is transferred to the transmitter unit and a magnetic field is generated proportional to the current by means of the transmitter coil. This magnetic field, also the target is located within, generates Eddy currents and causes regeneration of a magnetic field by the target.
Implementation Method 2
The controller provides taking of the definite integral of the waveform of the signal in predetermined intervals by means of the control signals applied to the synchronous integrator unit. The definite integral of the signal is being digitized in sampling unit, say, the ADC (analog to digital converter).
Data Source
AI summary
This invention is related to the method providing computation of the signal frequency components in an acceptable accuracy in contravention of the shifts in the phase and the magnitude information caused by asynchronous sampling of the signals in the process of asynchronous sampling of metal detectors wherein the received signal by the receiver unit (4) divided into time intervals, say timing values those are far shorter than the sampling period and correspond to nearest probable sampling of the ADC (6); providing the computation of the sine and cosine coefficients or exponents of time constant coefficients of the said timing value from previously located or dynamically generated coefficient table; resulting the elimination of the requirement of synchronous sampling and the requirement of the signal period is multiple of the sampling period.