Some applications of autonomous sensors can be founded in remote monitoring apparatus for the measurement and recording of physiological parameters [8-11]. 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. This technique allows, for example, real-time reading of glucose levels in diabetic patients, critical care and brain injuries. In orthopedic science autonomous sensors are used for accurate measurements of knee forces in total knee arthroplasty [1]. These forces produce wear in polyethylene, stress distribution in the implant and the implant�Cbone interface, and stress transfer to the underlying bone.

Autonomous sensors are adopted in many other fields: in the literature applications in harsh environments are described, such as under high temperatures, cold, humidity or corrosive conditions [12-17]; applications in which long distances are to be bridged or a big number of distributed components is necessary, such as smart homes, environmental applications [18] or mobile applications for the monitoring of environmental conditions [19]. Common examples of applications are the structural health monitoring of bridges or buildings [20] and the monitoring of climate conditions or pollution [21]. In environmental monitoring flow and temperature are important parameters for efficient control of domestic or industrial plants [22].

In these cases, temperature values along the sections of a heating or cooling plant are important indicators to control the energy efficiency in the regulation of thermal comfort [23-24].Usually an autonomous sensor requires a power source: several examples reported in literature are equipped with batteries, but other power sources are emerging such as: harvesting modules and inductive links. Since the voltage and current levels of the electronic circuits do not currently meet the possibility offered by power harvesting system or sometimes even by batteries, management of the power supply is required; this block commonly consists of a dedicated DC-DC converter and power supervision circuits. Several sensors are powered by rechargeable batteries [18-19]. However, batteries frequently dominate the size and weight of the device.

Batteries introduce unwanted maintenance burdens of replacement and, they often cannot be easily replaced since the autonomous sensor is placed in a protected environment. Moreover, GSK-3 the disposal of the increasing number of batteries is creating an important environmental impact as they contain toxic chemicals.Since autonomous sensors are wireless devices, they encounter the typical problems of a wireless network. If the distance between the wireless device and the data collection system is short, a point to point communication can be implemented.