Lexikon Aussteuerungsanzeige specifications

Category : Lexicon

Level indicators are used as an aid for the correct level setting of a device or system. This is a measuring device, the characteristics of which depend on the application. The characteristics can be the subject of standards. Common characteristics are VU and PPM.

With the VU meter, the scale goes from -20 to +3. It is a dB scale, the zero point of which is set at +4dBu, where the "red range"also begins. The measuring range consequently extends from -16dBu to +7dbu. A second scale goes from 0% to 100%, where 100% coincides with the zero point at 4dBu. The instrument is relatively sluggish and therefore can not follow fast signal peaks. It is therefore more suitable for approximately estimating the loudness of a sound signal. If you are faced with the task of monitoring the overload at short signal peaks, a different characteristic is necessary:

The PPM (Peak Program Meter) is 30 times as fast as the VU meter and therefore suitable for monitoring signal peaks. There are several different scales for PPM, as national standardization bodies have made different determinations here. In Germany, a scale standardized by DIN applies, which ranges from -50dB to +5dB, with the "red range" starting at 0dB. This zero point corresponds to a level of +6dBu. At -9dB there is a mark for a measuring level. Here, too, there may be another scale from 0% to 100%, with 100% falling to the zero point.

The meaning of the % scale on both instruments lies in the connection to broadcasting, and is intended to denote the degree of modulation. 100% Modulation refers to the maximum permissible modulation of the carrier signal, if it is exceeded, signal distortions and / or disciplinary measures by the monitoring authorities are to be feared.

The zero point (or 100% point) of the instruments does not usually denote the point at which the overdrive starts in a normal device. Almost all devices are more or less resistant to overdrive beyond this point. The zero point corresponds to the full level, which is the maximum level that should be reached in normal operation. It depends on the equipment class as well as on national customs or even individual working habits, how much reserve is available or desired in addition.

The level reached during normal operation is always below the level at full scale. The measurement level set by DIN at -9dB corresponds to the average level of "ordinary dance music", which is controlled in such a way that its peaks reach 0dB. This is a somewhat arbitrary definition, which obviously depends on the type of signal. The peak value factor (crest factor) of the signal is important as the measure of how high the peaks of the signal are in relation to the average signal level. This ratio dictates how far one has to stay below the full level with the normal level in order to avoid overdriving at signal peaks. The lower the factor, the closer you can get to the full level when controlling the normal level. The peak value factor can be limited with a limiter or dynamic processor, so you can increase the average level without getting into overdrive. But this can have tonal disadvantages.

See also the Wikipedia articles: VU-Meter, Peakmeter