Sensor Timestamping via Transmitted Time Difference Delta-t
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Solution Overview
Problem
Autonomous sensors with unsynchronized internal clocks face challenges in providing accurate timestamps for measurement data transmitted to synchronized receivers, due to significant clock drift and the absence of bidirectional communication links, which is crucial for precise management in energy and water distribution networks.
Innovation Solution
The sensors calculate and transmit the time difference between measurement and transmission instants, allowing the receiver to adjust the timestamp to a reference time base, ensuring accurate timestamping with an error of less than 30 seconds by subtracting the transmitted time difference from the reception instant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the sensor uses an unsynchronized internal clock to reduce cost and power consumption, then the sensor price and energy use decrease, but the timestamp accuracy of transmitted data deteriorates due to significant clock drift
Solution Approach 1:
The sensor performs preliminary actions by calculating and storing the time difference Δt between measurement instant t1 and transmission instant t2 before actual transmission occurs. This pre-computed time difference is then used by the receiver to accurately timestamp the measurement data, eliminating the need for continuous clock synchronization while maintaining timestamp precision.
Solution Approach 2:
The time difference Δt acts as an intermediary parameter that bridges the gap between the unsynchronized sensor clock and the synchronized receiver clock. By transmitting this intermediate value along with the measurement data, the receiver can compensate for clock drift and establish accurate timestamps without requiring bidirectional communication for synchronization.
2Device complexity
If the sensor transmits data periodically without clock synchronization to reduce complexity, then the device complexity decreases, but the ability to accurately manage and analyze measurement data deteriorates
Solution Approach 1:
The sensor performs self-service by autonomously calculating the time difference Δt between its internal clock's measurement instant and transmission instant. This self-computed time difference is then transmitted with the measurement data, enabling the receiver to accurately reconstruct measurement timestamps without requiring complex synchronization protocols or additional infrastructure.
3Duration of action of moving object
If the sensor accumulates data over long periods without synchronization to extend operation between transmissions, then the transmission frequency can be reduced, but the timestamp accuracy deteriorates due to cumulative clock drift
Solution Approach 1:
The sensor performs preliminary calculation of the time difference Δt at the moment of transmission, covering the entire accumulation period. This pre-computed Δt value encapsulates the total time elapsed between the first measurement instant t1 and the transmission instant t2, regardless of how long the accumulation period lasts, allowing accurate timestamping even after extended operation without synchronization.
Data Source
AI summary
System for transmitting data for remote logging between a measurement sensor (1a, 1b) comprising an electronic circuit with non-synchronized internal clock and a memory for storing at least one value measured at a first instant (t1), and a transmitter (7) suitable for transmitting at a second instant (t2) the value or values measured at the first instant (t1), and a receiver (12, 12a) synchronized to a reference time base, for gathering the measured values transmitted; the sensor (1a, 1b) comprising an electronic circuit suitable for establishing the time difference ?t (t2 - t1) between the instants of transmission (t2) and of measurement (t1) according to the internal clock of the sensor, and the transmitter (7) transmits, with the value or values measured at the first instant (t1), this time difference ?t; and the receiver comprises a circuit for subtracting from the reception instant (T0) according to the reference time base, the time difference (?t) transmitted via the transmitter so as to give the difference (T0 - ?t) as date to the measurements transmitted.