Eddy Current Array Multiplexing for Faster Nondestructive Inspection
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Solution Overview
Problem
Existing non-destructive inspection methods, such as eddy current probes, face limitations in inspection speed due to constraints in electronic sensing inputs and the use of Time Division Multiplexing (TDM), which restricts the maximum inspection speed, especially for low-frequency probes.
Innovation Solution
Combining Time Division Multiplexing (TDM) with Pulse-Amplitude Modulation (PAM) to reduce the number of time slots, allowing for faster channel switching and increased sampling frequency, thereby enhancing inspection speed without compromising signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Time Division Multiplexing (TDM) is used to switch between multiple sensors at each electronic input, then the number of sensors that can be monitored is increased, but the inspection speed is severely limited
Solution Approach 1:
The patent combines TDM with Pulse Amplitude Modulation (PAM) to create a hybrid multiplexing system. Multiple sensors are grouped into sets, with each set assigned to a unique PAM code. Within each time slot, multiple sensors can be simultaneously activated with different PAM codes, allowing parallel signal transmission through a single channel while maintaining sensor individuality and significantly increasing inspection speed compared to traditional sequential TDM switching.
2Productivity
If the number of electronic sensing inputs is limited, then device size and cost are reduced, but the ability to inspect surfaces faster is compromised
Solution Approach 1:
The patent introduces PAM codes as an intermediary layer between multiple sensors and a limited number of electronic inputs. Each sensor or group of sensors is assigned a unique PAM code that modulates its signal amplitude in specific time slots. This intermediary encoding scheme allows many more sensors to share fewer electronic inputs without requiring proportional increases in hardware complexity, enabling high-productivity inspection with compact, cost-effective devices.
3Measurement precision
If traditional TDM samples every sensor sequentially with each sensor allocated a time slot equal to the period of the excitation signal, then signal quality is maintained, but the measurement time increases
Solution Approach 1:
The patent implements periodic PAM-coded excitation signals where groups of sensors are activated in repeating time slots according to their assigned codes. This periodic structure allows the system to maintain signal quality through consistent sampling intervals while reducing total measurement time by parallelizing sensor activation. The periodic PAM sequences enable multiple sensors to be sampled simultaneously within each period, dramatically decreasing the time required to acquire data from all sensors compared to sequential TDM sampling.
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 significantly increases inspection speed by a factor equal to the number of input channels, enabling faster data acquisition and improved productivity while maintaining an acceptable signal-to-noise ratio.
Implementation Method 1
Eddy Current (EC) is a commonly used method for non-destructive testing and inspection (NDT/NDI)
Implementation Method 2
Eddy Current Array (ECA) probes use multiple sensors in order to increase the inspection coverage
Data Source
AI summary
A combination of pulse-amplitude modulation and time division multiplexing is used to increase the scan speed when performing non-destructive inspection, such as with an eddy current array.