Synchronized Measurement Device Using Local Area Network Ethernet Messaging
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Solution Overview
Problem
Existing systems for collecting dynamic data from distributed analog sensors face challenges with time synchronization due to phase delays and latency in networks, making it difficult to compare data from multiple sensors accurately.
Innovation Solution
A network architecture with a central processing unit, master clock, and Ethernet network switch that synchronizes sampling clocks across measurement devices using time synchronization messages over a dedicated channel, ensuring all data is collected simultaneously and in phase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If data is collected from multiple sensors using networked instrumentation devices, then remote data acquisition capability is improved, but time synchronization accuracy deteriorates due to phase delays and network latency
Solution Approach 1:
The system separates time-critical sampling clock functions from networked data transmission functions. Each sensor device maintains an independent sampling clock that operates autonomously without being affected by network latency, while data transmission occurs separately through the network. This segmentation allows remote data acquisition while preserving local timing precision.
Solution Approach 2:
The system implements a master-slave clock synchronization mechanism where the master clock distributes time reference signals to slave clocks through the network. Slave clocks use feedback from the master clock to adjust and synchronize their timing, compensating for network variations and maintaining accurate time synchronization across distributed sensors.
2Device complexity
If standard Ethernet networks are used for sensor data transmission, then device complexity is reduced, but time synchronization precision deteriorates due to network path length variations and congestion
Solution Approach 1:
The system divides the measurement function into two independent parts: local sampling clock operation and network data transmission. The sampling clock operates locally without network dependency, while data transmission uses standard Ethernet. This segmentation eliminates network-induced timing errors while maintaining simple network infrastructure.
Solution Approach 2:
The master clock acts as an intermediary that distributes synchronized time references to all slave clocks through the network. This intermediary mechanism ensures all sensors sample at synchronized times despite using simple standard Ethernet infrastructure, compensating for network path variations.
3Area of stationary object
If multiple sensors are distributed over a geographic area, then measurement coverage area is improved, but phase delay differences worsen due to varying network path lengths
Solution Approach 1:
The system separates the sampling function from the communication function. Each distributed sensor maintains its own sampling clock that operates independently of network distance, allowing wide geographic coverage. The segmentation enables sensors to be distributed over large areas while maintaining synchronized sampling through local clock operation.
Solution Approach 2:
The master-slave clock synchronization system provides feedback-based time correction to distributed slave clocks. Even though sensors are geographically dispersed with varying network path lengths, the feedback mechanism from the master clock ensures all slave clocks remain synchronized, maintaining phase coherence across the distributed array.
Data Source
AI summary
A plurality of measurement devices have analog sensors that measure the dynamic signals of physical events, sample the data into digital format with time synchronized clocks and generate time stamped Ethernet messages that are sent to a remote host. The remote host has a master clock that evaluates decoded time stamped messages from the measurement devices and sends back a message with a time correction error signal relative to the master clock. This feedback signal is used by the measurement devices to correct a local clock for data sampling and new message generation. Eight wire cable and associated connectors are used to handle three channels of traffic, with four wires dedicated to Ethernet messages as one channel, another two wires dedicated to reset and other commands as a second channel and another two wires to transmit power from the host to the measurement devices as a third channel.