Long-term, Time-synchronized Temperature Monitoring using Self-Powered CMOS Timers

In this paper, we propose a framework for time synchronized sensing of temperature with applications in supply-chain monitoring. At the core of the proposed framework is a chip-scale self-powered timing device that has been shown to be robust to manufacturing artifacts and has been shown to precisely track absolute time for years. In this paper we exploit two key characteristics of the timer device: its sensitivity to temperature, and its ability to synchronize time across multiple devices that are subjected to identical environmental conditions. Here, we also propose a mathematical model that captures the time-temperature behavior of the timers more accurately. Sensor/timer prototypes were fabricated on a standard 0.5 μm CMOS process and experiments were conducted in a thermally-controlled chamber with continuous monitoring using commercial-off-the-shelf (COTS) sensors. Results show that variations in the recovered temperature readings from our proposed framework were comparable to that of measured temperature using the COTS sensor. Due to its small form factor and robust behavior, we believe this sensor presents a solution for integrating and monitoring every individual samples in a supply-chain.