Use a triggered acquisition to synchronize an image acquisition with events external to the computer, such as receiving a pulse from a sensor that indicates the position of an item on an assembly line. The trigger signal must be connected to a trigger input of the image acquisition device. The triggered acquisition settings available in this step will vary based on the type of device you select in the Select Acquisition Source step and the acquisition type you select in the Select Acquisition Type step of the wizard. The Trigger Summary Table provides an overview of all the triggers configured for this acquisition.
Complete the following steps to configure a trigger line.
- Click the Add Trigger button to add a trigger to the Trigger Summary Table.
Tip Click the Remove Trigger button to remove a trigger from the Trigger Summary Table.
- Select the Line to use for the trigger signal.
- Use the Action control to specify the trigger type of the selected Line. The following options are available:
- Trigger Start of Acquisition—An acquisition begins when the specified trigger line detects the correct polarity edge.
- Trigger Every Image—Waits until the specified trigger line detects the correct polarity edge to acquire each image.
Note The NI 17xx also supports specifying a trigger delay. The delay units are milliseconds or, if quadrature encoders are supported, encoder counts.
- Trigger Start of Buffer List—When the assertion edge of a trigger is received, the buffer list is acquired. The first buffer always waits on a trigger before acquiring. This mode is only supported for the Continuous Acquisition with Inline Processing with the Acquire Image Type set to Acquire Every Image.
- Trigger Every Line—Waits to acquire each line from a line scan camera until the specified number of Skip Triggers edges have occurred. This mode only applies to line scan cameras.
- Trigger End of Acquisition—Stops the acquisition after Number of Post Trigger Buffers has been acquired after a correct polarity edge is detected on the specified trigger line. Returns an array of pre-trigger images and post-trigger images. This mode is only supported for the Continuous Acquisition with Inline Processing with the Acquire Image Type set to Acquire Every Image.
Note Not all hardware supports this feature.
- Trigger Height of Acquisition—Uses the trigger signal level to determine how long to acquire from a line scan camera. While the trigger line is in the active state, each line acquired will be added to the image height. When the trigger line becomes inactive, the resulting image is returned. This mode only applies to line scan cameras and cannot be used at the same time as Trigger Every Image.
Note The maximum height allowed is determined by the Acquisition Height specified in Measurement & Automation Explorer (MAX). Note Not all hardware supports this feature.
- Select a Polarity to define the active edge of the trigger. The following options are available:
- Rising Edge
- Falling Edge
- Specify a Timeout, in milliseconds, to wait for the active edge of a trigger to be received and the image to be captured.