GPS-Synchronized ADC Sampling for Precise Distributed Timestamping
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Solution Overview
Problem
Existing data acquisition systems face challenges in achieving sub-10 microsecond timestamping accuracy due to timing errors and latency issues, particularly when using satellite radio beacon positioning systems for synchronization, as they often result in unpredictable time stamping of live data streams across distributed remote sensor units.
Innovation Solution
A distributed data acquisition system that employs satellite radio beacon positioning systems for precise timestamping, utilizing a hardware logic circuit with a field programmable gate array to associate measurement data with absolute timestamps, and a central host processor for bias correction, ensuring accurate timestamping and synchronization of ADC sampling clocks across multiple units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If software-based timestamping is used in distributed data acquisition systems, then the system complexity is reduced, but the timestamping accuracy deteriorates to worse than 100 microseconds due to processor latency and interrupt service routine delays
Solution Approach 1:
The patent introduces an intermediary device - a Field Programmable Gate Array (FPGA) - that acts as a mediator between the GPS receiver and the data acquisition system. The FPGA receives GPS timing signals and generates precise trigger outputs that directly control the ADC sampling clocks, eliminating the need for software-based timestamping while achieving better than 10 microseconds accuracy. This intermediary hardware component resolves the contradiction by providing both the timing precision of hardware and the ease of software control.
2Measurement precision
If GPS satellite signals are used for synchronization across distributed units, then the absolute time reference is improved, but unpredictable timing errors and latency are introduced due to software processing delays
Solution Approach 1:
The patent replaces the software-based timing mechanism with a hardware-based timing mechanism using an FPGA. The FPGA directly processes GPS satellite signals and generates timing triggers through hardware logic, eliminating software processing delays and interrupt service routine latencies. This substitution of hardware for software ensures both the absolute time reference accuracy and the reliability of timing consistency across distributed units, achieving better than 10 microseconds accuracy.
3Area of stationary object
If distributed sensor units are physically separated by large distances, then the spatial coverage is improved, but the synchronization accuracy deteriorates due to lack of electrical hardware connection
Solution Approach 1:
The patent employs GPS satellite reception as a universal time reference that can be received by all distributed sensor units simultaneously regardless of their physical separation. Each unit independently receives the same GPS timing signals and uses the FPGA to generate synchronized sampling triggers based on this common reference. This universal time source enables wide spatial coverage while maintaining synchronization accuracy better than 10 microseconds across all distributed units.
Data Source
AI summary
A distributed data acquisition system comprising multiple, physically unconnected, data acquisition units that can be in wireless communication with a remote host, timestamps measurement data with sub-microsecond time base accuracy of sampling clock relative to an absolute timeframe. Each unit has a GPS receiver for deriving an absolute time. An analog-to-digital converter samples measurement data using a sampling clock. A hardware logic circuit, such as a field programmable gate array, associates batches of the measurement data with corresponding timestamps representing the current absolute time. A time offset bias may be compensated by a comparison of timestamps with nominal time based on start time and nominal sampling rate. Additionally, the sampling clock may be synchronized using time pulses from the GPS receiver. An initial start of ADC sampling by all data acquisition units may be also synchronized.