Digital Log Amplifier Ultrasonic Testing Dynamic Range
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Solution Overview
Problem
Ultrasonic inspection systems face challenges in detecting small defects near the surface of test objects due to the large dynamic range of signals, as analog logarithmic amplifiers are limited by noise and accuracy, making it difficult to distinguish small echo signals from the initial pulse.
Innovation Solution
A system using multiple linear amplifiers processes ultrasonic signals, converting them into digital signals with high-frequency sampling, and logic circuits combine the outputs to create a continuous linear digital signal with a wide dynamic range, allowing for accurate detection of small defects by eliminating the constant wave signal from the top surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If analog logarithmic amplifiers are used to compress the dynamic response range, then the signal compression is achieved, but noise and accuracy problems occur
Solution Approach 1:
The patent replaces analog logarithmic amplification with a digital signal processing system. Multiple linear amplifiers with different gain levels amplify the input signal, and a microprocessor selectively combines their outputs based on signal amplitude. This substitution of digital processing for analog logarithmic compression eliminates the noise and accuracy limitations of analog components while achieving the desired dynamic range compression.
Solution Approach 2:
The patent divides the signal processing function into multiple parallel channels, each with a linear amplifier having a different predetermined gain level. Instead of using a single analog logarithmic amplifier, the system segments the amplification task across multiple linear amplifiers (e.g., amplifiers with gains of 1, 10, 100), and a microprocessor selectively combines their outputs. This segmentation allows the system to maintain linearity in each channel while achieving overall logarithmic-like compression through digital selection and combination.
2Adaptability or versatility
If multiple linear amplifiers with different gain levels are used, then the dynamic response range is extended, but the device complexity increases
Solution Approach 1:
The patent merges the outputs of multiple linear amplifiers with different gain levels into a single combined output signal. A microprocessor monitors the output signals from all amplifiers and selectively combines them based on which amplifier provides the optimal signal level for the current input conditions. This merging approach allows the system to achieve an extended dynamic response range comparable to analog logarithmic amplifiers while maintaining the advantages of linear amplification.
Solution Approach 2:
The patent implements a dynamic selection and combination mechanism where a microprocessor continuously monitors the output signals from multiple amplifiers and adaptively selects which amplifier output to use or combine. This dynamic approach allows the system to optimize signal quality across a wide dynamic range by automatically adjusting which amplifier channel is active based on real-time signal conditions, thereby achieving versatility without requiring manual reconfiguration.
3Loss of information
If the echo signal from near-surface flaw is displayed concurrently with the initial pulse, then the complete signal is captured, but the small echo signal is masked by the large initial pulse
Solution Approach 1:
The patent applies different gain levels to different portions of the signal dynamic range through multiple parallel amplification channels. Each linear amplifier is configured with a specific gain level suitable for detecting signals of particular amplitude ranges. By having amplifiers with gains of 1, 10, 100, and other predetermined levels, the system ensures that whether the input signal is large (initial pulse) or small (near-surface flaw echo), there is always an appropriate amplifier channel that optimally amplifies that specific signal level without masking it.
Solution Approach 2:
The patent changes the gain parameter across multiple amplification channels to handle different signal amplitude levels. Instead of using a single fixed-gain amplifier or an analog logarithmic amplifier with limited bandwidth, the system employs multiple linear amplifiers with systematically varied gain parameters. A microprocessor monitors and selectively combines outputs from these amplifiers with different gain settings, allowing the system to adaptively optimize the gain parameter based on the actual signal amplitude, thereby preventing masking of small echo signals by large initial pulses while maintaining complete signal capture.
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 enables the detection of small defects near the surface and provides a wide dynamic response range for measuring signals from various depths, improving the accuracy of ultrasonic inspections by eliminating noise and distortion.
Implementation Method 1
a transducer containing a piezoelectric element is excited by an electrical pulse to transmit an ultrasonic pulse into a test object
Implementation Method 2
The transducer receives the reflected wave and the reflected wave is converted by the transducer into an electrical signal
Data Source
AI summary
The apparatus and method of the present invention provides a plurality of linear amplifiers simultaneously processing an ultrasonic signal. Each amplifier of the plurality of linear amplifiers has a predetermined gain level suitable for achieving the desired output signal level for input to an analog to digital (A/D) converter for processing. The output of each amplifier is sampled by each respective A/D converter at a very high frequency to convert the analog signal output of each of the linear amplifiers to a digital signal. Logic circuits simultaneously monitor all of the output digital signals from the A/D converters. The logic circuits determine which output of the A/D converters has the greatest linear output and stores the selected output in a memory storage device. The saved output waveforms are subsequently combined into a continuous linear digital output that has a dynamic response range that is approximately the sum of the individual dynamic response ranges of the individual amplifiers and A/D converters. The combined continuous linear digital output waveform may be input to a logarithmic conversion to produce a waveform having a wide dynamic range.