Abstract
Autonomous sensors play a very important role in the environmental, structural, and medical fields. The use of this kind of systems can be expanded for several applications, for example in implantable devices inside the human body where it is impossible to use wires. Furthermore, they enable measurements in harsh or hermetic environments, such as under extreme heat, cold, humidity or corrosive conditions. The use of batteries as a power supply for these devices represents one solution, but the size, and sometimes the cost and unwanted maintenance burdens of replacement are important drawbacks. In this paper passive and self-powered autonomous sensors for harsh or hermetical environments without batteries are discussed. Their general architectures are presented. Sensing strategies, communication techniques and power management are analyzed. Then, general building blocks of an autonomous sensor are presented and the design guidelines that such a system must follow are given. Furthermore, this paper reports different proposed applications of autonomous sensors applied in harsh or hermetic environments: two examples of passive autonomous sensors that use telemetric communication are proposed, the first one for humidity measurements and the second for high temperatures. Other examples of self-powered autonomous sensors that use a power harvesting system from electromagnetic fields are proposed for temperature measurements and for airflow speeds.
Highlights
Autonomous sensors can be defined as devices that autonomously execute their measurement functions in the measurement environment
Different characteristics are indicated: the calculated values are estimated in accordance with the data reported in the referenced papers. As it can be deduced from the Table, an autonomous sensor can rely on a budget of less than 1 mW from a generic power harvesting system
A passive autonomous sensor for high temperature measurement is represented schematically in Figure 7a) developed using the Metal MUMPs process [42] and a planar inductor realized in thick film technology by screen printing over an alumina substrate a conductive ink in a spiral shape
Summary
Autonomous sensors can be defined as devices that autonomously execute their measurement functions in the measurement environment They are unwired from the acquisition unit; they are characterized by autonomous power supplies and the ability to measure and transmit data. Autonomous sensors are increasingly used in many applications, mostly in measuring physical phenomena They can be applied for measurement of quantities both in mobile devices, or in protected environments, or in spaces where electrical energy is absent. Autonomous sensors are applied on live animals for analysis of brain stimulants to analyze neurochemical data for research purposes These systems are small and light enough to record biopotentials from awake birds and insects. The general architectures of passive and self-powered autonomous sensors are described and discussed
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