Mixed voltage

If you connect a DC voltage with an AC voltage , e.g. B. superimposed by series connection of two corresponding sources, a mixed voltage is created as the sum voltage . Mixed voltages are also created, for example, by pulsing a direct voltage on and off or by rectifying a sinusoidal alternating voltage; because tensions arise that contain an alternating component and a constant component (arithmetic mean) not equal to zero.

The designation as "direct voltage" is retained in many applications even with mixed voltages when the alternating voltage component is so small that it is of no significance for the intended use, and in particular when no sign changes occur.

When measuring with an oscilloscope , the curve shape of the mixed voltage is retained regardless of whether you are working in the AC or DC measuring range, while the height of the curve jumps when the AC / DC measuring range is switched. From a metrological point of view, this distinguishes it from alternating voltage, in which the display remains unchanged regardless of the AC or DC measuring range. This applies at least to a frequency above about 10 Hz.

When measuring with an indicating voltmeter , it should be noted whether it works in the DC voltage range to generate mean or effective values. In the alternating range, it should be noted whether it works with a rectifying value or an effective value, and whether it detects the entire mixed voltage or just its alternating component.

In the case of a mixed voltage, which is also referred to as direct voltage according to the prerequisite above, its mean value and its rectified value are the same (the rectified value, however, is displayed 11% too high); In the case of a mixed voltage with a change in sign, the rectified value has no information content. Without restriction, their effective value is greater than their mean value.

See also mixed flow .