peak program meter (PPM)
A peak meter is a level meter for audio peak voltages. It is similar to the VU meter, but differs in that it can display voltage peaks. Since the peak values displayed depend on the crest factor of the audio signals, significant differences occur in the displays of a peak meter and a VU meter depending on the signal shape.
Level meters are also called level meters and differ in precision and application. They can be simple pointer instruments, but also precision instruments with bar graph display and the possibility of adjustable headroom.
There are peak level meters, Peak Program Meters ( PPM) and quasi-peak level meters, Quasi Peak Program Meters (QPPM). Peak level meters are particularly suitable for displaying and storing levels and peak levels. In order to handle the short-term peak levels, peak meters are equipped with a peak hold function and a peak memory. The response time is based on human hearing behavior and is 10 ms for analog measurements and 1 ms for digitalmeasurements.
There are several standards - DIN, British, Nordic, EBU, Digital - that differ in scaling and are described under IEC 60268-10 for analog and IEC 60268-18 for digital instruments. The International Electrotechnical Commission (IEC) has specified the decay time of level meters as 1.5 seconds to a level of -20 dB.