Ultrasonic Flaw Detection with Multi-Gain A/D Conversion
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Solution Overview
Problem
Existing ultrasonic flaw detectors face challenges with complex analog front ends, leading to calibration difficulties, reliability issues, and inconsistent results due to variable gain nonlinearities, back wall attenuation, and DC offset errors, which affect the detection of internal structural faults in materials.
Innovation Solution
The development of a high dynamic range analog to digital conversion system that eliminates the need for a Variable Gain Amplifier (VGA) circuit, using three A/D converters with different gain channels to extend the dynamic range and compensate for signal skew errors, while implementing digital DC offset compensation to improve accuracy and readability of inspection results.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex analog front ends with multiple analog circuits are used, then the dynamic range and signal processing capability are improved, but the device complexity and calibration difficulty increase
Solution Approach 1:
The patent replaces complex analog circuits with a digital system consisting of a single A/D converter and digital signal processing. The analog front end is simplified to minimal analog components, with gain control and signal processing performed digitally. This substitution eliminates the need for multiple analog amplifiers, attenuators, and filters, thereby reducing device complexity while maintaining detection capability.
Solution Approach 2:
The patent changes the operating parameters of the A/D converter dynamically through digital gain selection. Multiple fixed gain channels (e.g., 0dB, 20dB, 40dB, 60dB) are provided, and the system digitally selects and combines these channels to achieve variable gain control. This parameter change approach replaces continuous analog gain adjustment with discrete digital gain levels, simplifying the analog circuitry while maintaining flexibility.
2Reliability
If variable gain amplifiers are switched in and out of the signal path, then the dynamic range is adjusted, but the gain linearity and calibration consistency deteriorate
Solution Approach 1:
The patent segments the gain control function into multiple fixed gain channels rather than using a single variable gain amplifier. Each channel has a predetermined, stable gain value (e.g., 0dB, 20dB, 40dB, 60dB). The system digitally selects and combines these segmented gain channels to achieve the desired overall gain, eliminating the need for continuous analog adjustment and improving gain linearity and calibration consistency.
3Productivity
If analog circuits are used with DC offset errors, then the signal processing is performed, but the waveform accuracy and measurement precision deteriorate
Solution Approach 1:
The patent replaces analog DC offset correction circuits with digital DC offset compensation. The single A/D converter captures the full signal including DC offsets, and digital signal processing algorithms subsequently remove the DC components. This digital approach eliminates the need for analog nulling circuits and provides more accurate DC offset removal, thereby improving waveform accuracy and measurement precision.
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 solution simplifies the calibration process, enhances the accuracy and consistency of ultrasonic inspection results by reducing noise and base line errors, and improves the detection of flaws near the back wall of the object, providing a more reliable and efficient ultrasonic inspection system.
Implementation Method 1
transmitting ultrasonic pulses to a target object and analyzing echo signals detected from the target object
Implementation Method 2
transmitting ultrasonic pulses to a target object and analyzing echo signals detected from the target object
Implementation Method 3
high dynamic range analog to digital conversion system that eliminates the need for a Variable Gain Amplifier (VGA) circuit, using three A/D converters with different gain channels
Data Source
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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.