An Automated measurement system for measuring an overall power efficiency and a characterisation of piezo harvesters

Systems for measurement power characteristics of piezo harvesters in dependence on a frequency and a load resistance are not commonly used due its complexity. Therefore, the parameters are usually measured manually near its resonant frequency. In some cases, it is convenient to measure the characteristics in a broader range of parameters. Then, in order to achieve more precise results and effective measurement we decided to develop our own measurement system. The system controls an effective value of vibrations, sets a frequency and a load resistance for measuring a power generated by a piezo harvester and measures a tip displacement of the harvester. These quantities are used for a characterisation of piezo harvesters. Moreover, the voltage and current on vibration exciter are measured to evaluate the overall efficiency of the harvester. The system was tested on a harvester MIDE PPA-1001 for various added weights and vibration levels from 0.1 to 0.5 g. The measured data analysed and the efficiency was calculated as a ratio between a vibration power consumed by the harvester and its electrical output. The evaluated overall efficiency varies between 10 and 15 % nearby its optimal working conditions