What are Pre- and PostTrigger?

• So that the memory is only filled by data with important meaning, the actual recording is only activated by a start signal (the so-called trigger signal). Each time the start signal becomes active, the data is recorded during the defined time and stored as a so-called event.
• So that the course of the signals can also be observed before and after the start time (trigger time), an event consists of three parts: The pre-history (recordings before the start time), the actual event and the post-history. The duration of the pre (pre) and post (post) histories can be defined in the device.
  

Especially the pre-trigger requires an additional explanation.

• As soon as the device is parameterized and the recording is started, the saving of the data begins. These data are written into a memory, which is overwritten again as soon as it is full. This overwriting of the ring memory lasts until a signal starts the actual recording (triggering). Thus the full prehistory is available in the memory at this time. The prehistory provides an indication of anomalies in the network that could be responsible for triggering the trigger signal (motor starting current).

• With the Mavowatt 30 the max. possible trigger setting is 100 periods (max. 30 periods pre and max. 100 post). It is just 20 sec., so it is totally unsuitable for the analysis of a motor starting current, because the starting process can take 1-2 minutes. Mavowatt 40 and 70 are able to capture 10000 periods (max 30 periods Pre and max 9998 Post), this corresponds to 3 minutes. Sufficient to analyze one start-up event.

• The duration of the recording of the actual event is determined by the trigger signal: As long as it is active, recording takes place. If the signal is very short, it is recorded for at least 80 microseconds, and if the signal is active for a very long time, recording is stopped after the maximum time (equal to the defined event time) (post-trigger). The event itself is recorded for one period. The event duration is identical to the defined event time, regardless of the length of the trigger signal. By the post history the consequences of a certain event become recognizable.

• The consequences can be as follows: Oscillations (dynamics) in the system, voltage fluctuations or voltage interruptions.