3.3.1.1.3 Trigger Controls

The Oscilloscope trigger sub-module helps to identify and lock on to only the portion of the input signal desired. Depending on the operating mode set by the run controls, the trigger can:

  • Lock on to a periodic signal and constantly update the plot

  • Only update the plot when the signal exceeds some level

Edge Triggering

The edge triggering mechanism is looking for the signal to cross the trigger level. For a positive edge trigger, the signal must go from below the trigger level, to above the trigger level.

Figure 3-14. Positive Edge Trigger
  1. No trigger – the line must cross.
  2. No trigger – wrong direction.
  3. Trigger point.
Figure 3-15. Negative Edge Trigger
  1. No trigger – the line must cross.
  2. No trigger – wrong direction.
  3. Trigger point.

Set the Edge Trigger Type

The trigger mechanism has two edge trigger modes: Positive and Negative Edge Trigger.

  • To set the Positive Edge Trigger mode, click the
    button. The button will be highlighted when activated.
  • To set the Negative Edge Trigger mode, click the
    button. The button will be highlighted when activated.

Set the Trigger Level

The trigger level can be adjusted in three different ways:

  • Enter a trigger level value into the text box. Press the TAB keyboard button or click the mouse outside the text box to let the new value take effect.

  • Click on the up/down arrows located to the right of the text box

  • With the mouse cursor positioned over the text box, scroll the mouse wheel to increase/decrease the trigger level setting

  • Drag the trigger level line in the plot area to a new position

Select the Trigger Source

The Oscilloscope trigger sub-module uses one of the channel signals when looking for the trigger condition.

  • Click the colored Trigger source button corresponding to the channel chosen for use as a trigger source. The active Trigger source button will be highlighted.

Set the Trigger Mode

The Oscilloscope module supports both Triggered and Free Running mode.
  • Click Normal to enable Triggered mode. The plot will only be updated when the trigger condition is satisfied.
  • Click Auto to enable Free Running mode. The plot will be updated continuously and the trigger conditions will be ignored.