Acquisition Memory Decimation for Continuous Signal Recording
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Solution Overview
Problem
Conventional test and measurement instruments, such as digital oscilloscopes, are limited by their memory capacity, leading to the inability to capture and store extended durations of input signals due to high data throughput requirements, resulting in missed data during triggering events and limited visibility of high-frequency signals.
Innovation Solution
The implementation of a test and measurement instrument with an acquisition memory that adapts by modifying the decimation rate of incoming and stored data, allowing continuous recording beyond initial memory capacity through decimation techniques, enabling the storage of extended signal durations without pre-configuration, and providing tools for controllable playback and data management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If memory capacity is increased to capture extended signal durations, then the ability to store longer signals improves, but the cost and complexity of the memory system increases
Solution Approach 1:
The memory system is divided into multiple circular buffers that operate independently. Each buffer can be configured with different record lengths and decimation rates, allowing the system to capture extended signal durations by sequentially using multiple buffers rather than requiring one large buffer. This segmentation reduces the complexity of managing a single large memory system while achieving the same extended capture capability.
2Measurement precision
If data throughput rate is increased to maintain high-frequency signal fidelity, then measurement precision improves, but memory capacity is consumed faster
Solution Approach 1:
The system dynamically adjusts the decimation rate based on the current buffer state and signal characteristics. When a buffer is nearly full, the system can increase decimation for that buffer while maintaining full-resolution capture in other buffers. This dynamic adjustment allows the system to maintain overall signal fidelity across extended time periods without uniformly consuming memory capacity at the maximum rate.
Solution Approach 2:
Different circular buffers can have different decimation rates applied to them simultaneously. Buffers capturing critical high-frequency content maintain lower decimation (higher fidelity), while buffers capturing less critical portions use higher decimation. This local quality approach preserves measurement precision where needed while managing memory capacity consumption across the extended recording period.
3Productivity
If trigger conditions are used to capture specific events, then relevant data capture efficiency improves, but data from between triggers is lost
Solution Approach 1:
The system continuously writes incoming signal data into multiple circular buffers without interruption, regardless of trigger conditions. While traditional systems pause or reset between triggers, this system maintains continuous operation across all buffers. Trigger conditions can still be applied to identify and analyze specific events of interest, but the continuous writing ensures that no inter-trigger data is lost, as all data is preserved in the sequential buffer structure.
4Duration of action of moving object
If record length is extended to capture more signal, then visibility of high-frequency signals improves, but data throughput requirements increase
Solution Approach 1:
The extended record length is achieved by segmenting the capture across multiple circular buffers rather than requiring a single continuous high-throughput write operation. Each buffer can be filled at the maximum data throughput rate, and the overall extended duration is achieved by concatenating or sequentially accessing multiple buffers. This segmentation allows the system to maintain high data throughput rates while achieving extended total capture duration.
Data Source
AI summary
A test and measurement instrument includes an acquisition memory and a processor structured to store a stream of sampled incoming data samples in the acquisition memory. As the memory fills, the instrument automatically decimates either the data samples already stored in the acquisition memory, the incoming data samples, or both. The instrument may also store two copies of the incoming data samples, one at an increased decimation rate. The two copies are tied together with a timestamp or using other methods. The more highly decimated copy may be used to produce a video output of the stored data samples, saving the instrument from generating the video output from the larger sized sample.