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This paper presents the theory, development, and results for a temperature sensing system that employs a wireless sensor with powering and communications based on inductive coupling. The theory of inductive coupling is presented along with a methodology that has been developed to determine the system elements in order to fulfill communication range and bandwidth requirements in a certain class of applications. A miniaturized wireless sensor was built (volume 3.2 cm3), and the whole system was validated by means of an experiment where the sensor was immersed in a water bath, in which the temperature was varied during 69 h in a cycle covering a span of 30°C. Measurements had a high correlation with an accurate reference thermometer. It is shown that the interruption of the radio frequency (RF) field during the measurements is a useful method to improving the measurement quality. In the course of the validation experiment, this method reduced the standard deviation of the measures up 0.01°C.
Date of Publication: Oct. 2011