Serial-Link Clock Synchronization for Electric Meters
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Solution Overview
Problem
Existing industrial electricity meters face challenges in synchronizing their internal clocks with UTC time in a cost-effective, secure, and simple manner, as current methods require additional ports or are vulnerable to hacking.
Innovation Solution
A synchronization method using a serial connection between the meter and external equipment, such as a modem, allows for precise resynchronization of the internal clock without additional hardware, utilizing existing serial connections and secure communication protocols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a dedicated TOP SYNCHRO signal port is used for clock synchronization, then synchronization precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent makes the existing serial communication port serve dual functions: both data communication and clock synchronization. By configuring the port in interrupt trigger mode during synchronization, it eliminates the need for a dedicated synchronization port while maintaining precision, thus reducing device complexity without sacrificing measurement precision.
Solution Approach 2:
The patent combines the clock synchronization function with the existing serial communication interface. The same physical port and communication protocol used for data exchange are repurposed to carry synchronization signals, merging two functions into one interface and reducing overall system complexity.
2Measurement precision
If NTP server with GPS or Ethernet link is used for synchronization, then synchronization precision is improved, but cost and security vulnerability increase
Solution Approach 1:
The patent uses a local serial communication interface as an intermediary between the meter and the synchronization source. This physical layer intermediary with limited communication capabilities (compared to network protocols) inherently reduces the attack surface and hacking vulnerability while still achieving precise synchronization through interrupt-driven timing.
Solution Approach 2:
The patent employs a simple, inexpensive serial communication protocol rather than complex network protocols like NTP over Ethernet or GPS. This simpler protocol is more secure against hacking because it lacks the complexity that would otherwise provide attack vectors, while still achieving the required synchronization precision through direct hardware-level timing signals.
3Device complexity
If existing serial connection is used for synchronization, then device complexity and cost are reduced, but synchronization precision may deteriorate
Solution Approach 1:
The patent dynamically configures the serial port between normal data communication mode and interrupt trigger mode for synchronization. This dynamic reconfiguration allows the same hardware interface to operate in different modes depending on the operational context, maintaining full precision capabilities while using existing infrastructure.
Solution Approach 2:
The patent establishes the interrupt trigger mode configuration in advance during the synchronization process. By preparing the port in the appropriate mode before receiving the synchronization signal, the system ensures that timing precision is maintained without requiring additional hardware, thus resolving the precision-complexity trade-off.
Data Source
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Figure 3
AI summary
A method for synchronizing a clock (9) of an electric meter (1) which includes a first processing unit (5) comprising a first port (8) arranged to be connected to an external device (2), comprising the steps of: ∘ receiving via the first port (8) a first frame containing a reference time; ∘ configuring the first port to operate in an interrupt trigger mode; ∘ receiving via the first port a pulse defining a synchronization time, and triggering an interrupt leading to the recording of the reference time as a current time at the synchronization time; ∘ reconfiguring the first port to communicate via the first port using the serial link.