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A piezoelectric power generator or harvester can convert impact energy from various mechanical vibrations of daily life into electrical energy. It is an environmentally friendly power generating system. Recently, battery powered RFID tags have attracted attention as a new technology for commodity identification and management in the ubiquitous computer society. However, the need for periodic battery exchange is a major disadvantage of such active RFID-tags. This study describes possible applications of piezoelectric generators to active RFID-tags. As examples of RFID-tag applications enabled by a piezoelectric generator, we propose a safety system to monitor children going to and returning from school as well as a network system to monitor the utilization of a conference room. Experimental results are presented.

A highly accurate, guarded series-resistors-type voltage divider has been developed for measuring direct voltages of the range of 10 V to 1000 V. A divider consists of wirewound bobbin resistors which are installed in a temperature regulated oil bath and supplied with 1 mA constant current by the 1000 V of a calibrator. The voltage ratios are determined by a self-calibration technique using 10 V and 100 V reference voltages. Typical relative uncertainty is several parts per 10 7 for self-calibration of voltage ratio of 1000 V to 10 V. A comparison of the voltage ratio calibrations between this system and that of National Metrology Institute of Japan showed a reasonable agreement.

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