Przegląd metod pomiaru małych energii dla oceny układów „energy-harvesting” i systemów mikromocowych

W artykule omówiono trzy metody pomiaru małych energii dla oceny układów zasilania typu „energy-harvesting” i systemów mikromocowych. Opisano klasyczną metodę techniczną, jak i estymację energii zarówno poprzez pomiar ładunku oraz wykorzystanie równoważenia ładunku. Niezależnie od metody pomiaru, zwrócono uwagę na specyficzny, impulsowy i nieregularny charakter poboru energii przez systemy mikromocowe oraz podobny impulsowy charakter energii wytwarzanej przez przetworniki energy harwester (EH).

The article is concern on the issues of measurement methods of small energy low-power devices which collecting the Energy avilable in the enviroment. The main difficulty in constructing such devices is an estimation of energy demand. The average power consumption the low-power system is typically calculated in microwatts. Accurate measurement of the energy consumed by a typical micropower system is problematic - measuring device must have a large dynamic range. It is assumed that the measured currents can be varied by at least two orders of magnitude. There must be a wide band width due to the fact that a large current is consumed in a very short time (pulse). Similar requirements determine the measurement of the Energy supplied from alternative sources. Electrical energy available at the output of converter usually appears irregularly in pulses of varying intensity of current and different voltages. For this reasons technical method and use of current-voltage converters are useless. The another method assumes sampling the signals of supply voltage and current and performing multiplication and integration numerically, but it have a number of drawbacks. Charge counting method gives more reliable results than the voltage and current measurement, even using high-speed A/D converters. Unfortunately, it is problematic to use the circuit in this form to measure the amount of energy generated by the EH source, because the measured current is flowing out of the system. The concept of measurement based on the principle of operation on the A/D converters to the load balancing is a bit more complicated in hardware implementation. The meter built according to the Figure 6 allows the measurement of the flow charge with an accuracy not worse than 2.5% on the highest resolution, and not worse than 1.2% for a resolution of 5 thousand plots. This type of device may measure the charge flowing in one direction, for example from the source to the battery.