An Energy-Efficient All-Dynamic Multiparameter Sensor for Battery-Less Smart Nodes in Agricultural Internet-of-Things

The increasing demand for efficient and sustainable agricultural practices underscores the importance of Agricultural Internet-of-Things (Agri-IoT). This integration of technology in agriculture facilitates precise and efficient farming methods, contributing significantly to global food security and environmental conservation. For Agri-IoT optimization, it is essential to obtain information such as temperature, ambient humidity (AH), and soil moisture (SM) in an environment-friendly manner. The existing sensor node is powered by a battery that can potentially pollute the soil and have a limited lifespan. In this work, we present a sensor chip that can efficiently read temperature, AH, and SM in an all-dynamic manner. The multiparameter chip operates in an event-driven manner, which only starts wireless transmission if an input event is detected. The event-driven operation further reduces the energy consumption of the sensor node. The low-energy sensor is combined with an RF energy harvester (EH) and wireless transmitter (TX) to achieve battery-less data acquisition. The proposed sensor chip is fabricated in 65-nm CMOS technology and occupies a chip area of 0.612 mm2. The measured temperature accuracy is
$\pm 1~^{\circ }$
C over the range of
$- 40~^{\circ }$
C–
$85~^{\circ }$
C with a single-point calibration. The measured AH ±3.8% RH over the 10%–90% RH range. Besides, it can support SM monitoring over the range of 10%–50% gravimetric water content (GWC). The power consumption of the multisensor interface circuits is
$4.8~\mu $
W at a supply voltage of 0.8 V.