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Triggering the Oscilloscope

Acquisition Types

To display acquired data in the Oscilloscope, you must click the Trigger button. You control how the data acquisition is initiated by specifying the acquisition type and the trigger type in the Trigger pane.

The Oscilloscope supports three acquisition types, which you select from the Acquire menu:

  • One Shot — Acquire the specified number of samples once.

  • Continuous — Continuously acquire the specified number of samples.

  • Sequence — Continuously acquire the specified number of samples, and use the dependent trigger type each time.

For each acquisition type, you can either fill the display with data or you can acquire a specific number of samples. Additionally, the specified trigger type determines how the acquisition is initiated.

Trigger Types

The Oscilloscope supports two trigger types, which you select from the Type menu:

  • Dependent — Data acquisition depends on the data. You define this dependency by specifying the hardware channel, trigger condition, trigger condition value, and whether pretrigger data is acquired.

    Note that you can specify a dependent trigger for only one channel at a time, and this channel initiates data acquisition for all other channels defined for the Oscilloscope.

  • Independent — Data acquisition starts immediately after you press the Trigger button, and is independent of the data. Note that the Sequence acquisition does not support this trigger type.

The Oscilloscope shown below is configured for a one-shot acquisition of 1000 samples for CH0 and CH1. The acquisition is dependent on the data, and is initiated when a rising signal level of -3.3 volts is detected on CH0. Additionally, the first 0.02 second of data is defined as pretrigger data.

When you use a dependent trigger type, the display associated with the selected channel contains these two indicators:

  • The trigger level on the vertical axis.

  • The location of the start of the trigger on the horizontal axis. The start of the trigger corresponds to the first acquired sample at time zero. As shown by the data tips for CH1, data to the left of the indicator is defined as pretrigger data and has negative time values.

Note that you can change the indicator locations graphically by placing the mouse cursor over the indicator and sliding it to the desired location.

Configuring Trigger Properties

You can change the characteristics of the labels associated with the Triggers pane with the Scope Editor GUI. To open this GUI, select Scope from the Edit menu, choose the Scope Properties pane, and select Triggers from the Select the scope components list box. The Scope Properties pane is shown below.

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