nullspannungsu00fcbergangsdetektor and procedure for determining the nullspannungsu00fcbergangspunktes

摘要

A zero crossing detector (9) including an analyser (13) adapted to determine a zero level crossing of a currently input electrical pulse packet and to output a trigger signal indicative of a determination having been made; and a pre-trigger unit (12) adapted to monitor variations in the amplitude of the currently input pulse packet to detect a crossing of a pre-trigger level. The detector (9) further comprises a control means (11) operably connected to the pre-trigger unit (12) and adapted to compare the amplitude of the pre-trigger level with an amplitude of a signal derived from one or other of the currently or a previously input electrical pulse packet and to automatically control the amplitude of the pre-trigger level provided to the pre-trigger unit (12) to maintain a working difference. IMAGE