Pretriggering and Posttriggering of Scopes

By default, the scope starts acquiring data at the same time as the trigger event (the trigger point). Sometimes, to observe the values that led to the trigger, you start acquiring data a given number of samples before the trigger event (pretriggering). Other times, to observe the system settling after the trigger, you delay acquiring data a given number of samples after the trigger event (posttriggering).

Use the NumPrePostSamples scope property to specify pretriggering and posttriggering. A negative value indicates pretriggering and a positive value indicates posttriggering. For example, suppose that P is the value of NumPrePostSamples for Scope 1 and TP is the trigger point, the sample where the trigger event occurs.

  • P = 0 — Scope 1 starts acquiring data immediately at trigger point TP.

  • P < 0 — Scope 1 starts acquiring data |P| samples before trigger point TP.

  • P > 0 — Scope 1 starts acquiring data P samples after trigger point TP.