Multiplexed ADC Sampling for Multi-Probe NDI Instruments
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Solution Overview
Problem
Non-destructive inspection (NDI) instruments face challenges in accommodating multiple probe types with different sensor elements, bandwidths, and sampling rates, leading to increased size, cost, and power requirements due to the need for multiple analog-to-digital converters, making it impractical to add more converters for additional probes.
Innovation Solution
A multiple mode digitization system using a single set of analog-to-digital converters with a multiplexing block and phase adjusters to compensate for signal propagation delays, allowing for interleaved sampling and different sampling rates without requiring multiple clock frequencies, thereby reducing the need for dedicated converters for each probe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple analog-to-digital converters are added to accommodate multiple probe types with different sensor elements and sampling rates, then the instrument can support more probe inputs and maintain simultaneous sampling, but the size, cost, and power requirements of the instrument increase significantly
Solution Approach 1:
The patent merges multiple probe inputs into a single analog-to-digital converter by using time-division multiplexing. The converter processes signals from multiple probes sequentially at different time intervals, effectively combining the function of multiple converters into one device while maintaining the ability to handle different probe types and sampling rates
Solution Approach 2:
The analog-to-digital converter is designed to be universal by accepting multiple probe inputs with different characteristics (number of sensor elements, bandwidths, sampling rates). The converter performs multiple functions by dynamically configuring its operation mode based on which probe is currently being processed, eliminating the need for dedicated converters for each probe type
2Measurement precision
If dedicated analog-to-digital converters are provided for each probe input, then simultaneous sampling of all signals is achieved, but the instrument becomes overly large, expensive, and power-intensive
Solution Approach 1:
The system uses periodic action by implementing time-division multiplexing where the single analog-to-digital converter alternates between processing signals from different probes in periodic time slots. This allows the converter to be activated only when needed for each probe, reducing overall power consumption compared to having multiple continuously active converters
Solution Approach 2:
The patent creates a time-copied version of simultaneous sampling by sequentially capturing signals from multiple probes at different time instances. The system reconstructs the simultaneous sampling effect through digital processing of these time-separated samples, eliminating the need for multiple physical converters operating in parallel
3Speed
If the sampling rate is increased for high bandwidth probes, then real-time signal analysis capability is improved, but the number of analog-to-digital converters required increases
Solution Approach 1:
The system implements dynamics by allowing the analog-to-digital converter to dynamically adjust its sampling rate based on the specific probe being processed. When a high bandwidth probe is connected, the converter operates at higher sampling rates; when lower bandwidth probes are used, it operates at lower rates, optimizing performance while avoiding the need for multiple fixed-rate converters
Data Source
AI summary
A multiple mode digitization system for a non-destructive inspection instrument which makes use of a multiplexing circuit and a single set of analog to digital converters to efficiently digitize analog test signals from a plurality of inputs. In the preferred embodiment, each of the analog to digital converters in the system is driven with an independent and separate clock signal, allowing for propagation delay compensation among the plurality of test signals as well as interleaved sampling such that custom sampling rates can be used for each input without the need for more than one clock frequency. In an alternate embodiment, phase adjustments on the sampling clocks are used only for interleave sampling, and digital filters are used to provide signal propagation delay compensation.