For the evaluation of voltage, current and power values, the root mean square value, which is the effective value, and the arithmetic mean value are used. From a mathematical point of view, the arithmetic mean corresponds to the sum of all values or measured values divided by their number. The arithmetic mean is calculated in statistics. In measurement technology
, it is often given together with the standard deviation. It stands for the mean of all values, whereas the standard deviation indicates the range of variation of the values. The arithmetic mean is the average value. It can refer to physical values such as temperature or pressure, to social developments such as the average number of births over a certain period of time, or to economic success factors such as the average turnover or profit over a certain period of time. The individual values are always cumulated and divided by the number. The result is the arithmetic mean.
In the case of changing physical quantities, such as an alternating voltage, the arithmetic mean is the area under the time function over a whole period. For a square wave signal with equal high, equal wide, but opposite voltage values, the positive and negative areas under the square wave function add up to a mean value of zero. It is different if the zero line is not in the middle between the two rectangles, but corresponds to the previous negative voltage level, for example. Then the rectangular signal has only positive polarity and the area corresponds to half the voltage amplitude.
In the case of a sinusoidal oscillation, the arithmetic mean value results from the positive and negative half-wave. Since both rectification values are equal in magnitude but have opposite polarity, the two areas add up to a mean value of zero.