USB Transducer Time Synchronization Circuit
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Solution Overview
Problem
Existing multi-channel data acquisition systems using USB hubs face challenges in synchronizing the time of data conversion for multiple transducers, particularly for applications requiring precise timing like shock and vibration measurements, where existing solutions are either complex or not sufficiently accurate.
Innovation Solution
A self-synchronizing transducer appliance with a time-synchronization circuit that includes a local oscillator, parser circuit, frequency and phase comparator, and trigger module, which generates a synchronization reference signal to ensure all A/D converters operate at the same clock frequency and phase, allowing for simultaneous data conversion across multiple channels connected to the same USB hub.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If multiple transducers share the same USB hub for data acquisition, then device complexity and cost are reduced, but time synchronization accuracy deteriorates
Solution Approach 1:
A USB synchronization hub is introduced as an intermediary device between the USB host and multiple transducers. The hub receives timing information from the host and distributes synchronized timing signals to all connected transducers, enabling precise time synchronization while maintaining the simplicity of sharing a common USB hub infrastructure.
Solution Approach 2:
The synchronization system implements feedback mechanisms where the USB hub monitors timing signals from the host computer and adjusts the distribution of timing information to multiple transducers. This feedback loop ensures that all transducers maintain synchronized timing despite variations in USB communication delays or hub processing times.
2Measurement precision
If a complex synchronization circuit is implemented to achieve precise timing, then time synchronization accuracy is improved, but device complexity increases
Solution Approach 1:
Each transducer is equipped with an internal clock and timing circuit that autonomously generates and maintains synchronization signals. The transducers self-synchronize by receiving periodic timing packets from the USB hub and adjusting their internal clocks accordingly, eliminating the need for complex external synchronization circuitry while maintaining microsecond-level timing accuracy.
Solution Approach 2:
The synchronization system uses periodic timing packets transmitted at regular intervals through the USB hub to synchronize all transducers. This periodic action allows transducers to continuously align their timing without requiring complex continuous synchronization circuits, achieving accurate timing through simple periodic updates.
Data Source
AI summary
A circuit and method of analog data acquisition synchronization from an analog sensor in multiple channels associated with a USB hub. An analog to digital converter connected to the sensor that is part of a USB device has a time and phase corrected sampling clock that is referenced to a start-of-frame traffic signal with a preconfigured message indicating a time offset or delay seen upstream through a USB port. A plurality of similar devices are autonomously synchronized by the same message for multi-channel data acquisition by a locally generated trigger signal that allows a preset amount of delay set by the message. An accelerometer is a preferred sensor for such multi-channel data acquisition.