Ultrasonic Flaw Detection ADC Architecture for Extended Dynamic Range
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Solution Overview
Problem
Existing ultrasonic flaw detectors face challenges due to their complex analog front ends, which lead to calibration issues, reliability problems, and inconsistent results, particularly in detecting faults near the back wall of an object, and require extensive calibration and maintenance.
Innovation Solution
A high dynamic range analog to digital conversion system that eliminates the need for a Variable Gain Amplifier (VGA) circuit by using multiple A/D converters with adjustable sample times and DC offset compensation, allowing for accurate and consistent signal processing across different gain channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple A/D converters with different gains are used to extend dynamic range, then measurement precision is improved, but device complexity increases due to multiple conversion channels
Solution Approach 1:
The patent divides the analog signal into multiple gain channels (first gain channel, second gain channel, third gain channel) before A/D conversion. Each channel processes the signal at a different gain level, allowing the system to capture both small and large amplitude signals with appropriate precision. This segmentation resolves the contradiction by achieving extended dynamic range through structured signal division rather than using a single complex converter.
Solution Approach 2:
The patent introduces gain control circuits as intermediary elements between the analog input and A/D converters. These intermediaries adjust the signal amplitude to match the optimal input range of each A/D converter, ensuring accurate conversion across the full dynamic range. The gain control circuits act as mediators that prevent both signal loss and overflow conditions.
2Adaptability or versatility
If Variable Gain Amplifier (VGA) circuit is used to adjust signal levels, then adaptability is improved, but reliability deteriorates due to calibration and maintenance issues
Solution Approach 1:
The patent extracts the gain control function from a single VGA circuit and distributes it across multiple fixed-gain amplifier channels. Each channel has a predetermined gain value, eliminating the need for continuous VGA calibration. This extraction of the variable gain function into discrete fixed-gain stages resolves the reliability issue while maintaining adaptability through digital channel selection.
Solution Approach 2:
The system employs automatic channel selection logic that monitors signal levels and automatically switches between gain channels based on the detected amplitude. This self-service mechanism eliminates manual calibration requirements and ensures the appropriate gain channel is always active without user intervention, improving both reliability and ease of operation.
3Adaptability or versatility
If analog circuits are switched in and out of signal path to adjust gain, then adaptability is improved, but manufacturing precision deteriorates due to impedance matching issues
Solution Approach 1:
The patent designs each gain channel with universal impedance characteristics that remain consistent regardless of which channel is active. The analog switches and amplifier stages are configured to maintain constant input and output impedances, ensuring that frequency response and impedance matching remain stable across all gain settings. This multi-functional design resolves the contradiction by making the impedance characteristics independent of the active gain channel.
4Measurement precision
If DC offset nulling is performed manually to center waveform, then measurement precision is improved, but ease of operation deteriorates due to complex calibration procedures
Solution Approach 1:
The patent incorporates automatic DC offset compensation circuits that continuously monitor and correct baseline shifts without user intervention. The system self-adjusts the DC level of each gain channel to maintain proper waveform positioning on the display. This automated approach resolves the contradiction by eliminating manual calibration steps while maintaining precise waveform positioning through continuous electronic correction.
Data Source
AI summary
A method and apparatus for effecting ultrasonic flaw detection of an object processes an echo signal received from the object being tested in at least three signal channels, wherein the echo signal is scaled to different degrees along each channel to increase and extend the dynamic range of an associated A/D converter system, in a manner which dispenses with the need for using numerous analog high pass and low pass filters and a variable gain amplifier. This reduces complexity and avoids performance limitations. The digital to analog converters sample the differently scaled input signal and a selection circuit selects the output of the digital output obtained from that analog to digital converter which has the highest gain, but which has not overflowed. The digital outputs are seamlessly merged to produce an output that can be displayed as a scan display which shows the location of faults.